Spindle unit

Abstract

To prevent generation of vibration in a spindle during machining.SOLUTION: Air pressure to be supplied for forming a radial air bearing is made lower than air pressure to be supplied for forming a thrust air bearing, by a pressure adjusting unit 114. That is, when a wafer is ground by a grindstone 23, a flow rate of the air supplied to a radial-side air ejection port 32 is reduced by the pressure adjusting unit 114, whereby the pressure of the air in a radial gap 300 is made lower than the pressure of air in a thrust gap 301. This allows a spindle 10 and the grindstone 23 to slide in a radial direction. As a result, since impact received by the spindle 10 can be alleviated, vibration is less likely to be generated in the spindle 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a spindle unit.

Background Art

[0002] As disclosed in Patent Document 1, a grinding apparatus for grinding a wafer held on a chuck table with a grinding wheel has a grinding wheel in which the grinding wheel is annularly arranged on an annular base mounted at the tip of a spindle, and grinds the wafer with the rotating grinding wheel by rotating the spindle.

[0003] As disclosed in Patent Document 1, a spindle unit for rotating a spindle includes a casing surrounding the spindle, fills a gap between the spindle and the casing with high-pressure air to form a thrust air bearing and a radial air bearing, and rotatably supports the spindle.

[0004] In recent years, in order to shorten the grinding time for grinding a wafer, etc., the load applied from the grinding wheel to the wafer has been increased. Also, during grinding, a part of the annular grinding wheel is brought into contact with the radial portion of the wafer. Therefore, due to the increase in load, the spindle is likely to tilt. Thus, in order to prevent the spindle from tilting even when the load is increased, the gap forming the thrust air bearing and the radial air bearing is narrowed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the spindle, which is rotatably supported by thrust air bearings and radial air bearings formed in a narrow gap, can vibrate when slight shocks are transmitted, such as when the grinding wheel contacts the wafer or when abrasive grains detach from the grinding wheel. Furthermore, this vibration is difficult to eliminate because it resonates through the air bearings. In addition, the vibration is difficult to eliminate because abrasive grains continue to detach quantitatively.

[0007] Therefore, in the grinding method disclosed in Patent Document 2, the grinding wheel is moved in a direction away from the wafer. However, while this grinding method can eliminate vibration by reducing the amount of abrasive grains that fall off, it increases the grinding time.

[0008] Therefore, the object of the present invention is to suppress vibration during processing in a spindle unit that rotatably supports a spindle to which a processing tool such as a grinding wheel for grinding wafers is attached at the tip. [Means for solving the problem]

[0009] The spindle unit of the present invention (this spindle unit) A spindle unit in which a spindle, to which a workpiece processing tool is attached at the tip, is surrounded by a casing, and a thrust air bearing and a radial air bearing are formed in the gap between the outer surface of the spindle and the inner surface of the casing, thereby rotatably supporting the spindle, wherein the workpiece rotates together with the spindle and moves together with the spindle unit in the direction of the rotation axis of the spindle to process the workpiece at the tip side, and when the workpiece is being processed by the workpiece, in the direction of the rotation axis of the spindle The thrust direction orthogonal to radial Equipped with a sliding mechanism that allows sliding in that direction, The spindle comprises a first disc portion and a second disc portion extending in the radial direction, The casing is An annular portion formed to fit between the first disc portion and the second disc portion of the spindle , the spindle Between the first disc portion and the second disc portion in side The annular portion is provided so as to face the side of the spindle and the annular portion Between It is a gap. It is open towards the radial gap, The spindle is supported in the radial direction by blowing air in the radial direction toward the radial gap. The radial air bearing In the radial gapTo form of A radial side air outlet, a first air supply passage for supplying air to the radial side air outlet, a radial side intake port arranged to sandwich the radial side air outlet, and a first exhaust passage connected to the radial side intake port for exhausting air from the radial gap, The annular portion is provided so as to face the first disc portion and the second disc portion, and the first disc portion and the second disc portion and the annular portion Between A gap and two connected to the radial gap It is open towards the thrust gap. By blowing air in the thrust direction toward the two thrust gaps, the radial air bearing is connected to and supports the spindle in the thrust direction. The thrust air bearing In the thrust gap To form of The slide mechanism comprises a thrust-side air outlet, a second air supply passage for supplying air to the thrust-side air outlet, a thrust-side intake port positioned to sandwich the thrust-side air outlet, and a second exhaust passage connected to the thrust-side intake port for exhausting air from the thrust gap. The system includes a pressure adjustment unit located in the first air supply passage, which adjusts the pressure of the air supplied to the radial gap to form the radial air bearing to be lower than the pressure of the air supplied to the thrust gap to form the thrust air bearing, or reduces the flow rate of the air supplied to the radial side air outlet via the first air supply passage. The air pressure in the radial gap is made lower than the air pressure in the thrust gap. In this spindle unit, the sliding mechanism may include the thrust air bearing and the radial air bearing having a wider gap than the thrust air bearing. In this spindle unit, the sliding mechanism forms the radial air bearing, which is made of a metal with a Vickers hardness of 50 to 100. The side surface of the spindle between the first disc portion and the second disc portion, or the surface of the annular portion facing the side surface. It may include. [Effects of the Invention]

[0010] This spindle unit is equipped with a sliding mechanism that allows the spindle to slide in a direction perpendicular to the direction of its rotation axis. This allows the spindle to slide when the grinding wheel comes into contact with the workpiece or chips, thereby mitigating the impact on the spindle. Consequently, vibrations in the spindle can be suppressed. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing the configuration of the spindle unit. [Figure 2]It is an explanatory diagram showing an enlarged view of the configuration near the annular portion of the casing. [Figure 3] It is an explanatory diagram showing an enlarged view of the configuration near the annular portion of the casing.

Embodiments for Carrying Out the Invention

[0012] The spindle unit 1 shown in FIG. 1 is provided in, for example, a grinding device and is used for grinding a wafer as a workpiece held on the chuck table of the grinding device. As shown in FIG. 1, the spindle unit 1 includes a spindle 10 in a vertical posture, a casing 30 that covers the spindle 10 and supports the spindle 10, a spindle cover 50 that covers the lower end portion of the spindle 10, and a rotation motor 60 that rotationally drives the spindle 10.

[0013] The spindle 10 is arranged to extend in the Z-axis direction, which is the direction of the rotation axis A1 shown in FIG. 1. A large-diameter first disk portion 11 is formed in the middle portion of the spindle 10. Also, a large-diameter second disk portion 12 is formed at the lower end portion of the spindle 10.

[0014] A rotation motor 60 is connected to the upper end of the spindle 10. The rotation motor 60 has a rotor 61 provided at the upper end portion of the spindle 10 and a stator 62. By applying a predetermined voltage to the stator 62, the rotor 61 rotates, and the spindle 10 rotates about its rotation axis A1.

[0015] Also, the stator 62 is provided on the inner peripheral surface of the casing 30 via a cooling jacket 65. A number of cooling water channels 66 are formed in the cooling jacket 65. The rotation motor 60 is cooled by these cooling water channels 66.

[0016] A rotation detection sensor 67 is provided near the upper end of the spindle 10 in the casing 30. The rotation detection sensor 67 is positioned to face a detected part 68 attached to the upper end of the spindle 10. The rotation detection sensor 67 is configured to detect the rotation of the spindle 10 by detecting the rotational movement of the detected part 68.

[0017] A wheel mount 20 is connected to the tip (lower end) of the spindle 10. The wheel mount 20 is formed in a disc shape and is fixed to the tip of the spindle 10. The wheel mount 20 supports the grinding wheel 21.

[0018] The grinding wheel 21 is formed so that its outer diameter is approximately the same as the outer diameter of the wheel mount 20. The grinding wheel 21 includes an annular wheel base 22 made of a metal material. Multiple grinding wheels 23, which are approximately rectangular in shape, are fixed to the underside of the wheel base 22 around its entire circumference. In this way, the grinding wheels 23 are mounted on the tip of the spindle 10.

[0019] The grinding wheel 23 is an example of a workpiece tool and is arranged in an annular shape on the lower surface of the wheel base 22. The grinding wheel 23 is rotated by the rotary motor 60 via the spindle 10, wheel mount 20, and wheel base 22. This allows the grinding wheel 23 to grind a wafer held on a chuck table (not shown) in a grinding apparatus equipped with the spindle unit 1, for example.

[0020] A grinding water inlet passage 131, which communicates with a grinding water source 130, is attached to the upper end of the spindle 10. The grinding water inlet passage 131 is also connected to a grinding water channel 132 provided within the spindle 10, wheel mount 20, and wheel base 22. With this structure, grinding water from the grinding water source 130 is supplied to the grinding wheel 23 via the grinding water inlet passage 131 and the grinding water channel 132.

[0021] The casing 30 has, for example, a substantially cylindrical shape, and is configured to house the spindle 10 and the rotary motor 60, etc. The top of the casing 30 is closed by a cover member 25. The casing 30 surrounds the spindle 10 and is configured to support the spindle 10 so that it can rotate freely with radial air bearings and thrust air bearings.

[0022] The casing 30 is provided with an annular portion 31 at its lower end. The annular portion 31 is provided on the casing 30 so as to fit between the first disc portion 11 and the second disc portion 12 of the spindle 10, and so as to create a small gap between the first disc portion 11 and the second disc portion 12 and the annular portion 31.

[0023] Furthermore, as shown in Figures 1 and 2, the casing 30 is provided with a radial-side air outlet 32 ​​in the annular portion 31, which constitutes a radial air bearing. This radial-side air outlet 32 ​​is connected to a first air supply passage 111 which is connected to an air supply source 110. Figure 2 shows an enlarged view of the vicinity of the annular portion 31 in the casing 30 shown in Figure 1, on the +X direction side.

[0024] The first air supply passage 111 is formed to extend from the outside of the spindle unit 1 into the interior of the annular portion 31 of the casing 30, and includes a pressure adjustment section 114 provided on the surface of the annular portion 31. This pressure adjustment section 114 will be described later.

[0025] The radial air outlet 32 ​​is connected to the first air supply passage 111. The radial air outlet 32 ​​is provided on the radial casing surface 36 of the annular portion 31 of the casing 30, which extends in the Z-axis direction, and is positioned opposite the radial spindle surface 13 of the spindle 10, which extends between the first disc portion 11 and the second disc portion 12. The radial spindle surface 13 of the spindle 10 is an example of the outer surface of the spindle 10. The radial casing surface 36 of the casing 30 is an example of the inner surface of the casing 30.

[0026] The radial air outlet 32 ​​opens toward the radial gap 300, which is the gap between the radial spindle surface 13 of the spindle 10 and the radial casing surface 36 of the casing 30. The radial air outlet 32 ​​ejects high-pressure air supplied from the first air supply passage 111 in a horizontal direction, which is the radial direction, toward this radial gap 300, thereby forming a radial air bearing in the radial gap 300 between the casing 30 and the spindle 10, which rotatably supports the spindle 10 with air without contact.

[0027] Furthermore, as shown in Figures 1 and 3, the casing 30 is provided with a thrust-side air outlet 35 in the annular portion 31, which constitutes a thrust air bearing. This thrust-side air outlet 35 is connected to a second air supply passage 112 that is connected to an air supply source 110. Figure 3 shows an enlarged view of the vicinity of the annular portion 31 in the casing 30 shown in Figure 1, on the -X direction side. The second air supply passage 112 is formed to extend from the outside of the spindle unit 1 into the inside of the casing 30, which includes the annular portion 31.

[0028] The thrust-side air outlet 35 is connected to the second air supply passage 112. The thrust-side air outlet 35 is provided on two thrust-side casing surfaces 37, which are the upper and lower surfaces of the annular portion 31 of the casing 30, so as to face the lower surface 15 of the first disc portion 11 and the upper surface 16 of the second disc portion 12 of the spindle 10. The lower surface 15 of the first disc portion 11 and the upper surface 16 of the second disc portion 12 of the spindle 10 are examples of the outer surfaces of the spindle 10. The thrust-side casing surfaces 37 of the casing 30 are also examples of the inner surfaces of the casing 30.

[0029] The thrust-side air outlet 35 opens toward the thrust gap 301, which is the gap between the lower surface 15 of the first disc portion 11 and the upper surface 16 of the second disc portion 12 of the spindle 10 and the two thrust-side casing surfaces 37 of the casing 30. The thrust-side air outlet 35 ejects high-pressure air supplied from the second air supply passage 112 toward this thrust gap 301 in the Z-axis direction, which is the thrust direction. This forms a thrust air bearing in the thrust gap 301 between the casing 30 and the spindle 10, which rotatably supports the spindle 10 with air without contact.

[0030] In this way, the spindle unit 1 surrounds the spindle 10, which has a grinding wheel 23 (a workpiece) attached to its tip, with a casing 30. A thrust air bearing and a radial air bearing are formed in the gap between the outer surface of the spindle 10 and the inner surface of the casing 30, thereby supporting the spindle 10 so that it can rotate.

[0031] Furthermore, as shown in Figures 2 and 3, the casing 30 is provided with a radial-side intake port 40 on the radial-side casing surface 36 of the annular portion 31, which opens toward the radial gap 300. The radial-side intake port 40 is connected to a first exhaust passage 115, indicated by a dashed line. The first exhaust passage 115 is provided to extend into the annular portion 31 and, as shown in Figure 2, is in communication with a radial air bearing exhaust port 116 provided on the surface of the annular portion 31. These radial-side intake port 40, the first exhaust passage 115, and the radial air bearing exhaust port 116 are used to discharge air from the radial gap 300.

[0032] Furthermore, the casing 30 is provided with a thrust-side intake port 41 on the thrust-side casing surface 37 of the annular portion 31, which opens toward the thrust gap 301. The thrust-side intake port 41 is connected to a second exhaust passage 117, indicated by a dashed line. The second exhaust passage 117 is provided so as to extend into the annular portion 31 and is in communication with a thrust air bearing exhaust port 118 provided on the surface of the annular portion 31. These thrust-side intake port 41, second exhaust passage 117, and thrust air bearing exhaust port 118 are used to discharge air from the thrust gap 301.

[0033] Furthermore, as shown in Figure 1, the spindle unit 1 has a control unit 7. The control unit 7 controls the operation of the spindle unit 1 by controlling each of the components of the spindle unit 1 described above.

[0034] Furthermore, the spindle unit 1 is equipped with a sliding mechanism that allows it to slide in the radial direction, which is perpendicular to the direction of the rotation axis A1 of the spindle 10, when the wafer, which is the workpiece, is being processed by the grinding wheel 23.

[0035] Specifically, the spindle unit 1 is equipped with the aforementioned pressure adjustment unit 114 as a sliding mechanism. This pressure adjustment unit 114 lowers the air pressure supplied to form the radial air bearing to a lower pressure than the air pressure supplied to form the thrust air bearing.

[0036] In other words, the pressure adjustment unit 114 is located in the first air supply passage 111 and is a valve for adjusting the flow rate of air supplied from the air supply source 110 to the radial side air outlet 32 ​​via the first air supply passage 111. As a result, the pressure adjustment unit 114, for example under the control of the control unit 7, reduces the flow rate of air supplied to the radial side air outlet 32 ​​when the wafer is being ground by the grinding wheel 23, thereby lowering the air pressure in the radial gap 300 to lower than the air pressure in the thrust gap 301.

[0037] In the spindle unit 1, when grinding a wafer with the grinding wheel 23 positioned at the tip of the spindle 10, the side and bottom surfaces of the grinding wheel 23 come into contact with the wafer and grind it. Therefore, vibrations may occur in the spindle 10 due to the impact that the wafer delivers to the side or bottom surface of the grinding wheel 23. In addition, if processing debris containing abrasive grains that have fallen off the grinding wheel 23 is not discharged from the vicinity of the grinding wheel 23, the processing debris may come into contact with the grinding wheel 23, causing the spindle 10 to be impacted and resulting in vibrations in the spindle 10.

[0038] In this regard, as in this embodiment, by lowering the air pressure in the radial gap 300 that forms the radial air bearing supporting the spindle 10 using the pressure adjustment unit 114, the spindle 10 and the grinding wheel 23 can slide in the radial direction. As a result, when the spindle 10 is subjected to an impact, the spindle 10 can slide in the radial direction, mitigating the impact on the spindle 10, and thus reducing the likelihood of vibration occurring in the spindle 10.

[0039] Furthermore, when the spindle 10 and the grinding wheel 23 slide in the radial direction, the grinding wheel 23 does not move away from the wafer, which is the workpiece, during grinding, so the grinding process is not interrupted. Therefore, in this embodiment, it is possible to suppress the generation of vibration of the spindle 10 while suppressing an increase in grinding time.

[0040] Furthermore, as the spindle 10 and grinding wheel 23 slide radially, machining debris containing abrasive grains that have fallen off the grinding wheel 23 can be easily discharged from the vicinity of the grinding wheel 23. This makes it possible to suppress vibrations of the spindle 10 more effectively.

[0041] Furthermore, the spindle unit 1 may include, in place of or in addition to the pressure adjustment unit 114, a thrust air bearing that supports the spindle 10 in the thrust direction, and a radial air bearing that supports the spindle 10 in the radial direction and has a wider gap than the thrust air bearing, as a sliding mechanism that enables the spindle 10 to slide in the radial direction. That is, the radial gap 300 in which the radial air bearing is formed may have a wider gap than the thrust gap 301 in which the thrust air bearing is formed.

[0042] In this case, the radial gap 300 forming the radial air bearing becomes relatively wide, and the volume for storing air in the radial gap 300 increases, so the air pressure in the radial gap 300 tends to decrease more easily. Therefore, when the spindle 10 is subjected to a radial force, the spindle 10 can slide in the radial direction. As a result, as described above, the impact on the spindle 10 can be mitigated, and vibrations in the spindle 10 become less likely to occur.

[0043] Furthermore, to make the radial gap 300 in which the radial air bearing is formed wider than the thrust gap 301 in which the thrust air bearing is formed, the spindle 10 may be made thinner to widen the radial gap 300. Alternatively, the thickness (size in the Z-axis direction) of the annular portion 31 in the casing 30 may be increased to narrow the thrust gap 301.

[0044] Furthermore, the spindle unit 1 may include, in place of or in addition to the radial air bearing having a wider gap than the pressure adjustment section 114 and / or the thrust air bearing, the outer wall of the spindle 10 (radial-side spindle surface 13) or the inner wall of the casing 30 (radial-side casing surface 36) that forms the radial air bearing, which is made of a metal with a Vickers hardness of 50 to 100, as a sliding mechanism that enables the spindle 10 to slide in the radial direction.

[0045] In other words, it is preferable that the radial-side spindle surface 13, which is the outer wall of the spindle 10 surrounding the radial gap 300 in which the radial bearing is formed, or the radial-side casing surface 36 of the annular portion 31 in the casing 30, is formed from a relatively soft metal with a Vickers hardness of 50 to 100.

[0046] In this regard, when the spindle 10 is subjected to an impact, a stronger-than-usual pressure is applied to the radial gap 300 that constitutes the radial air bearing. If the radial-side spindle surface 13 or radial-side casing surface 36 that constitutes this radial gap 300 is formed from a soft metal as described above, when a strong pressure is applied to the radial gap 300, the radial-side spindle surface 13 or radial-side casing surface 36 undergoes elastic deformation, and the radial gap 300 temporarily widens.

[0047] Therefore, as described above, the air pressure in the radial gap 300 tends to decrease relatively easily, allowing the spindle 10 to slide in the radial direction. This reduces the impact on the spindle 10, making it less likely for vibrations to occur in the spindle 10.

[0048] Furthermore, the elastically deformed radial spindle surface 13 or radial casing surface 36 will return to its original shape as the pressure in the radial gap 300 decreases. In this case, examples of metals with a Vickers hardness of 50 to 100 that constitute the radial spindle surface 13 or the radial casing surface 36 include copper alloys, zinc alloys, and aluminum alloys. [Explanation of symbols]

[0049] 1: Spindle unit, 7: Control unit, 10: Spindle, 11: First disc section, 12: Second disc section, 13: Radial spindle surface, 15: Bottom surface, 16: Top surface, 20: Wheel mount, 21: Grinding wheel, 22: Wheel base, 23: Grinding wheel, 25: Lid member, 30: Casing, 31: Annular part, 32: Radial side air outlet, 35: Thrust-side air outlet, 36: Radial-side casing surface, 37: Thrust side casing surface, 40: Radial side intake port, 41: Thrust side intake port, 50: Spindle cover, 60: Rotary motor, 61: Rotor, 62: Stator, 65: Cooling jacket, 66: Cooling water channel, 67: Rotation detection sensor, 68: Detected part, 110: Air supply source, 111: First air supply passage, 112: Second air supply passage, 114: Pressure adjustment section, 115: First exhaust passage, 116: Radial air bearing exhaust port, 117: Second exhaust passage, 118: Thrust air bearing exhaust port, 130: Grinding water source, 131: Grinding water inlet, 132: Grinding water channel, 300: Radial gap, 301: Thrust gap, A1: Rotating shaft

Claims

1. A spindle unit that rotatably supports a spindle, the spindle of which a workpiece processing tool is attached to the tip, is surrounded by a casing, and a thrust air bearing and a radial air bearing are formed in the gap between the outer surface of the spindle and the inner surface of the casing, The machining tool rotates with the spindle and moves with the spindle unit in the direction of the spindle's axis of rotation, machining the workpiece at its tip. The workpiece is being processed by the workpiece, and the workpiece is equipped with a sliding mechanism that allows sliding in a radial direction perpendicular to the thrust direction, which is the direction of the rotation axis of the spindle. The spindle comprises a first disc portion and a second disc portion extending in the radial direction, The casing is An annular portion formed to fit between the first disc portion and the second disc portion of the spindle, A radial air outlet is provided on the annular portion of the spindle so as to face the side surface between the first disc portion and the second disc portion, and is open toward the radial gap which is the gap between the side surface of the spindle and the annular portion, and is for forming a radial air bearing in the radial gap that supports the spindle in the radial direction by blowing air toward the radial gap in the radial direction, A first air supply passage for supplying air to the radial side air outlet, A radial air intake port is positioned so as to sandwich the radial air outlet, A first exhaust passage connected to the radial side intake port for exhausting air from the radial gap, A thrust-side air outlet is provided in the annular portion so as to face the first disc portion and the second disc portion, and is open toward two thrust gaps which are the gaps between the first disc portion and the second disc portion and the annular portion and are connected to the radial gap, and by ejecting air in the thrust direction toward the two thrust gaps, a thrust air bearing is formed in the thrust gap which is connected to the radial air bearing and supports the spindle in the thrust direction, A second air supply passage for supplying air to the thrust-side air outlet, A thrust-side air intake port is positioned so as to sandwich the thrust-side air outlet, It comprises a second exhaust passage connected to the thrust side intake port for exhausting air from the thrust gap, The sliding mechanism includes a pressure adjustment unit located in the first air supply passage. The pressure adjustment unit lowers the air pressure in the radial gap to the air pressure in the thrust thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the thrust gap to the Spindle unit.

2. The sliding mechanism includes the thrust air bearing and the radial air bearing having a wider gap than the thrust air bearing. The spindle unit according to claim 1.

3. The slide mechanism is made of a metal with a Vickers hardness of 50 to 100, and includes the surface of the annular portion facing the first disc portion or the spindle forming the radial air bearing, between the first disc portion and the second disc portion. The spindle unit according to claim 1.

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