Spindle Unit

Abstract

To provide a spindle unit capable of preventing residence of processing fluid including processed waste, in a gap between a cover and a spindle.SOLUTION: A spindle unit 6 comprises: a casing 62 which surrounds a spindle 60 whose axial direction is a vertical direction, forms an air bearing and supports the air bearing; a cover 65 in which a mount 73 is coupled to a tip of the spindle 60 protruding downward from a lower end of the casing 62, and which provides a gap 6027 between the cover and an external side face of the spindle 60 exposed to a space between the lower face of the casing 62 and the top face of the mount 73, and surrounds the spindle; and an air supply part 66 which is formed in the spindle 60, and supplies air into the gap 6027 by rotation of the spindle. The air supply part 66 has; an entry path 667 which is open to an upper part of the spindle 60, and extends in the axial direction; a radiation path 663 which extends in a radial direction of the spindle 60 from a lower end of the entry path 667, is open to an external side face of the spindle 60, and is communicated with the gap 6027. Air sucked from the opening at the top part of the rotating spindle 60 passes through the entry path 667 and the radiation path 663 and is released to the gap 6027 to clean the gap 6027.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, as disclosed in Patent Document 1, a grinding device that uses a grinding wheel to grind a workpiece held by a chuck table has an annular grinding wheel attached to a mount connected to the tip of a spindle, and the workpiece is ground with the grinding wheel that rotates as the spindle rotates.

[0003] The spindle unit that rotatably supports the spindle thus comprises a casing that surrounds the upright spindle, a thrust air bearing and a radial air bearing that are configured with high-pressure air supplied between the casing and the spindle, and a mount that is connected to the tip of the spindle that protrudes from the bottom of the casing and on which the grinding wheel is attached. The spindle unit also configures the thrust air bearing with a large area so that it can withstand the large vertical load in the axial direction of the spindle during grinding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-222003 Summary of the Invention [Problem to be solved by the invention]

[0005] The spindle unit exhausts the air that makes up the thrust air bearing from the side of the spindle, and is equipped with a cover to protect this outlet from machining debris.

[0006] However, there is a problem in that machining fluid containing machining debris enters the gap between the spindle and the cover, and then as the machining fluid dries, the machining debris adheres to the inner surface of the cover and the outer surface of the spindle, making it impossible to rotate the spindle. Therefore, in the spindle unit, there is a problem of preventing machining fluid containing machining debris from remaining in the gap between the spindle and the cover. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a spindle unit comprising: a spindle having an axial direction in the vertical direction and connected to a mount at the tip of which a processing tool is attached; and a casing that surrounds the spindle and forms an air bearing by injecting air from the inner surface thereof to rotatably support the spindle, wherein the mount is connected to the tip of the spindle that protrudes downward from the bottom end of the casing, and the top end is attached to the bottom surface of the casing; The lower end does not contact the upper surface of the mount, a cover surrounding the outer surface of the spindle with a gap between the outer surface of the spindle and the lower surface of the casing and the upper surface of the mount; and an air supply unit formed inside the spindle for supplying air to the gap as the spindle rotates, the air supply unit including an inlet passage opening at an upper portion of the spindle and extending in the axial direction of the spindle, and a radial passage extending from a lower end of the inlet passage in the radial direction of the spindle, opening at the outer surface of the spindle and communicating with the gap, wherein the rotation of the spindle causes air in the radial passage to be released into the gap by centrifugal force, generating negative pressure in the inlet passage, and the air is sucked in from the opening at the upper portion of the spindle, and the air that has passed through the inlet passage and the radial passage is released into the gap. The air passes through the gap between the bottom end of the cover and the top surface of the mount, The spindle unit cleans the gap.

[0008] In the spindle unit according to the present invention, it is preferable that exhaust air from the air bearing is introduced into the gap. [Effects of the Invention]

[0009] The spindle unit of the present invention comprises a spindle having an axial direction in the vertical direction and connected to a mount at its tip for attaching a processing tool, and a casing that surrounds the spindle and sprays air from its inner surface to form an air bearing to support the spindle rotatably. The mount is connected to the tip of the spindle that protrudes downward from the lower end of the casing, and a cover that surrounds the spindle exposed between the lower surface of the casing and the upper surface of the mount, leaving a gap between the outer surface of the spindle and the cover; and an air supply unit formed inside the spindle that supplies air to the gap as the spindle rotates. The air supply unit comprises an inlet passage that opens at the top of the spindle and extends in the axial direction of the spindle, and radial passages that extend from the lower end of the inlet passage in the radial direction of the spindle, open on the outer surface of the spindle, and lead to the gap. As the spindle rotates, air is sucked in from the opening at the top of the spindle, and the air that has passed through the inlet passage and the radial passages is released into the gap, making it possible to clean the gap. In other words, by rotating the spindle, air can be sent into the gap between the cover and the outer surface of the spindle, allowing grinding water mixed with grinding chips that has entered the gap to be expelled from the gap, and it is also possible to prevent rotation problems such as grinding chips adhering between the outer surface of the spindle and the inner surface of the cover, causing the spindle to scrape.

[0010] The spindle unit of the present invention introduces the exhaust air from the air bearing into the gap between the cover and the outer surface of the spindle, thereby making it possible to more reliably expel grinding water mixed with grinding chips that has entered the gap, thereby preventing rotation problems such as spindle galling. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a grinding mechanism including a spindle unit according to the present invention. [Figure 2] 1 in a case where a plurality of entrance passages are formed at equal intervals in the circumferential direction of the spindle. FIG. [Figure 3]2 is a cross-sectional view taken along a1-a2 of the spindle unit shown in FIG. 1 when the entrance path has a circular cylindrical shape in plan view. FIG. [Figure 4] 10 is a cross-sectional view illustrating a radiation path that faces the cover of the spindle and opens on the outer surface of the attachment part of the spindle so as to slope downward from the inside to the outside. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1 shows a grinding mechanism 7 that grinds a workpiece such as a semiconductor wafer held on a chuck table (not shown). The grinding mechanism 7 includes a spindle unit 6 according to the present invention, a mount 73 connected to the tip (lower end) of a spindle 60 that constitutes the spindle unit 6, and a grinding wheel 74, which is a processing tool attached to the lower surface of the mount 73. The processing tool attached to the underside of the mount 73 may be, for example, a CMP polishing pad or a dry polishing pad attached via a platen, or a cutting tool that cuts the workpiece while rotating it.

[0013] The grinding wheel 74, which is fixed to the underside of the circular plate-shaped mount 73 by bolts (not shown) or the like, includes a wheel base 742 and a plurality of roughly rectangular parallelepiped segments arranged in a ring shape on the bottom surface of the wheel base 742. The segments are formed by, for example, fixing diamond abrasive grains or the like with a resin bond or a vitrified bond. The plurality of annularly arranged segments form an annular grinding stone 743. Note that a circular grinding stone with no gaps, i.e., a grinding stone with a so-called continuous arrangement, may also be arranged on the underside of the wheel base 742.

[0014] Inside the mount 73, a grinding water distribution path 733 that communicates with the grinding water supply source 629 and serves as a path for grinding water is formed, entering the interior from the top surface and branching radially into multiple paths inside. In addition, on the underside of the wheel base 742, multiple injection ports 746 are formed that open at equal intervals in the circumferential direction, communicate with the grinding water distribution path 733, and inject grinding water mainly toward the inner surface of the grinding wheel 743. The grinding water injected from the injection ports 746 is supplied to the contact area between the grinding wheel 743 and the workpiece (not shown), such as a semiconductor wafer, to clean and cool the contact area.

[0015] The spindle unit 6 comprises a spindle 60 having an axial direction in the vertical direction (Z-axis direction) and connected to a mount 73 at its tip (lower end) for mounting a grinding wheel 74, and a casing 62 that surrounds the spindle 60 and sprays air from its inner surface to form an air bearing and rotatably support the spindle 60.

[0016] 1, the spindle 60, which is supported without contact by the casing 62, includes a cylindrical long shaft portion 600 extending in the Z-axis direction, a circular plate portion 601 formed integrally with the long shaft portion 600 at a midpoint of the long shaft portion 600 and extending radially outward from the long shaft portion 600, and a circular plate-like attachment portion 602 extending radially outward from the long shaft portion 600 on the lower side of the long shaft portion 600, to which the mount 73 is attached. A small gap is formed between the plate portion 601 and the attachment portion 602 and the inner surface of the casing 62.

[0017] 1, an in-shaft water flow path 609, which passes through the center of rotation and serves as a path for grinding water, is formed penetrating in the Z-axis direction inside the spindle 60. The in-shaft water flow path 609 is connected to a grinding water distribution path 733 formed in the mount 73.

[0018] The upper end of the long shaft portion 600 of the spindle 60 passes through the center of the top plate 620 of the casing 62, and a pipe joint 6204, for example, is provided above the upper end of the long shaft portion 600. A water supply pipe 625 supported by the pipe joint 6204 is inserted into an in-shaft water flow path 609 of the spindle 60. A grinding water supply source 629, which is composed of a pump or the like and can supply grinding water (e.g., pure water), is connected to the upper end of the water supply pipe 625. If the processing mechanism in which the spindle unit 6 is provided is a polishing mechanism, a polishing liquid supply source, instead of the grinding water supply source 629, is connected to the in-shaft water flow path 609.

[0019] As shown in FIG. 1, for example, a casing 62 having an outer shape formed in a generally cylindrical shape forms an air bearing therein that supports the spindle 60 in a non-contact manner using the pressure of air supplied from an air supply source 69 such as a compressor.

[0020] The specific structure of the air bearing will now be described. An annular plate-shaped air injection part 621 is disposed at the bottom end of the casing 62 shown in Fig. 1 so as to fit between the plate part 601 and the mounting part 602 of the spindle 60. Small gaps that serve as air passages are provided between the plate part 601 of the spindle 60 and the air injection part 621 of the casing 62, between the mounting part 602 of the spindle 60 and the air injection part 621, and between the outer surface of the long shaft part 600 of the spindle 60 and the air injection part 621. A large number of injection ports (not shown) are formed on the outer surfaces (upper, lower, and inner peripheral surfaces) of the air injection part 621, and each injection port is connected to the air supply source 69 via an air flow path 6213 in the air injection part 621 and external piping.

[0021] 1 passes through the air flow path 6213 and is sprayed from each nozzle of the air spray unit 621 through a gap onto the outer surface of the spindle 60, whereby the spindle 60 is floatingly supported relative to the casing 62 via the high-pressure air. As a result, a radial air bearing and a thrust air bearing are formed within the casing 62, and the outer surface of the spindle 60 is rotatably supported in the radial and axial directions by the radial air bearing and the thrust air bearing. At this time, the plate portion 601 and the mounting portion 602 of the spindle 60 are floatingly supported over a wide range by the thrust air bearing, so that the processing load (vertical load) acting on the spindle 60 in the thrust direction (Z-axis direction) is appropriately distributed.

[0022] 1 is a motor including, for example, a rotor 632 connected to the side surface of the upper end of the long shaft portion 600 of the spindle 60, and a stator 634 disposed outside the rotor 632 on the inner surface of the casing 62 via a water-cooled radiator 633. A power supply (not shown) is connected to the stator 634, which supplies a predetermined amount of power to the rotational drive source 63. When a voltage is applied to the stator 634, the rotational drive source 63 rotates the rotor 632, thereby rotating the spindle 60 to which the rotor 632 is attached. The water-cooled radiator 633 suppresses heat generation from the rotational drive source 63.

[0023] The attachment portion 602 at the tip end (lower end) of the spindle 60 protrudes entirely downward from the lower end of the casing 62, and the mount 73 is connected to the flat lower surface of the attachment portion 602.

[0024] The spindle unit 6 includes a cover 65 that surrounds the spindle 60 exposed between the lower surface of the air injection portion 621, which is the lower surface of the casing 62, and the upper surface of the mount 73 facing it in the Z-axis direction, with a gap 6027 between the outer surface of the spindle 60, i.e., the outer surface 6024 of the mounting portion 602 in this embodiment, and an air supply portion 66 that is formed inside the spindle 60 and supplies air to the gap 6027 as the spindle 60 rotates.

[0025] The cover 65 is formed, for example, in a cylindrical shape, and its upper end side is connected to the lower surface of the air injection part 621. A gap 6027 formed between the outer surface 6024 of the attachment part 602 and the inner surface of the cover 65 is very small, for example, about several mm.

[0026] The air supply section 66 has an inlet passage 667 that opens at the top of the spindle 60 and extends in the axial direction (Z-axis direction) of the spindle 60, and a radial passage 663 that extends from the lower end 668 of the inlet passage 667 in the radial direction of the spindle 60, opens on the outer surface of the spindle 60, and leads to the gap 6027.

[0027] 1 and 2, a plurality of entrance passages 667 (for example, 12 in the example shown in FIG. 2) having a circular cross section are formed at equal intervals in the circumferential direction of the long shaft portion 600 of the spindle 60, and their upper ends open to the upper end surface of the long shaft portion 600. A lower end 668 of the entrance passages 667 is located inside the mounting portion 602. Note that FIG. 2 is a cross-sectional view taken along the a1-a2 line of the spindle unit shown in FIG. 1.

[0028] 3. The air supply section 66 may be provided with an inlet passage 666 instead of the inlet passage 667. The inlet passage 666 is formed in an annular shape around the long shaft portion 600 of the spindle 60 in the circumferential direction.

[0029] 1 and 2, the radial paths 663 extend radially from the center of the long shaft portion 600 in the radial direction of the plurality of spindles 60, and each have an outlet 6637 opening on the outer surface 6024 of the mounting portion 602. In the example shown in FIGS. 1 and 2, the shape of the outlet 6637 is a circle with the same diameter as the pipe diameter of the radial path 663. For example, the pipe diameter of the radial path 663 is set to be larger than the size of the gap 6027.

[0030] Instead of the radial paths 663, the air supply unit 66 may include radial paths 669 shown in Fig. 4. The radial paths 669 communicate with the lower ends 668 of the inlet paths 667 and extend radially in the radial direction of the multiple spindles 60 around the center of the long shaft portion 600, and each have an outlet 6697 opening on the outer surface 6024 of the mounting portion 602. As shown in Fig. 4, the outer surface 6024 of the mounting portion 602 below the outlet 6697 is formed so as to gradually widen while sloping downward from the inside to the outside. The centrifugal force generated by the rotation of the spindle 60 causes the grinding water mixed with grinding chips that has entered between the lower inclined surface of the outer surface 6024 and the inner surface of the cover 65 to be discharged.

[0031] 1, an air suction port 622 opens in a region slightly toward the outer periphery from the center of the top plate 620, and an opening that becomes the upper end of the entrance path 667 is located near and diagonally below the air suction port 622. Note that, although only one air suction port 622 is formed in the illustrated example, multiple air suction ports 622 may be formed, for example, at equal intervals around the periphery of the top plate 620.

[0032] The operation of the grinding mechanism 7 shown in FIG. 1 when grinding a workpiece such as a semiconductor wafer will be described in detail below. The chuck table (not shown) holding the workpiece moves horizontally to below the grinding mechanism 7. Then, the grinding wheel 743 of the grinding mechanism 7 and the workpiece held on the chuck table (not shown) are aligned.

[0033] Next, the grinding mechanism 7 is lowered by a grinding feed unit (not shown) including a ball screw, a motor, etc., and grinding is performed by the grinding wheel 743, which rotates in conjunction with the rotation of the spindle 60, which is supported in a contactless manner by an air bearing formed in the casing 62 as described above, coming into contact with the workpiece. During grinding, the workpiece held on the chuck table also rotates as the chuck table (not shown) rotates, for example, in the same direction as the grinding wheel 743, so that the entire upper surface of the workpiece is ground by the grinding wheel 743.

[0034] 1 supplies grinding water to the in-shaft water flow path 609 in the spindle 60 for cooling the grinding wheel 743. The grinding water supplied to the in-shaft water flow path 609 passes through the grinding water distribution path 733 of the mount 73, is sprayed out from each nozzle 746 of the grinding wheel 74, and reaches the contact point between the grinding wheel 743 and the workpiece. This grinding water cools the grinding wheel 740 and the workpiece, and also washes away grinding chips from the top surface of the workpiece together with the grinding water that has become waste processing liquid.

[0035] Conventionally, the grinding water mixed with the grinding chips would splash and get into the gap 6027 between the cover 65 and the outer surface 6024 of the mounting part 602, and then as the grinding water dried, the grinding chips would adhere to the inner surface of the cover 65 and the outer surface of the mounting part 602 of the spindle 60, causing the spindle 60 to become unable to rotate. However, in the spindle unit 6 according to the present invention, as the spindle 60 rotates, air 9 is sucked into the multiple entrance paths 667 from the openings of the entrance paths 667 in the upper end surface of the long shaft portion 600. That is, air 9 is sucked into the casing 62 from air suction ports 622 formed in the top plate 620 of the casing 62 located near and above the openings of the entrance paths 667 in the upper end surface of the long shaft portion 600 of the rotating spindle 60, and enters the entrance paths 667. The air 9 then flows down each entrance path 667 and along each radial path 663 from the center of the spindle 60 outward. Even if the inlet passage formed in the longitudinal shaft portion 600 of the spindle 60 of the air supply section 66 is an inlet passage 666 formed in a circular ring shape that goes around the longitudinal shaft portion 600 of the spindle 60 in the circumferential direction as shown in Figure 3, air 9 is similarly sucked in from the opening at the upper end of the inlet passage 666 by the rotation of the spindle 60.

[0036] 1 is discharged toward the gap 6027, thereby cleaning the gap 6027. That is, the grinding water containing grinding chips that has entered the gap 6027 can be discharged from the lower end of the gap 6027 to the outside of the cover 65 by the air 9 sent into the gap 6027.

[0037] In this way, the spindle unit 6 of the present invention can rotate the spindle 60 to send air 9 through the inlet path 667 and the outlet path 663 into the gap 6027 between the cover 65 and the outer surface of the mounting portion 602 of the spindle 60, so that grinding water mixed with grinding chips that has entered the gap 6027 can be discharged from the gap 6027, and rotation problems such as grinding chips adhering between the outer surface of the mounting portion 602 of the spindle 60 and the inner surface of the cover 65 will not occur.

[0038] In this embodiment, the exhaust air constituting the air bearing inside the casing 62 is introduced into the gap 6027. That is, during grinding, the high-pressure air that is ejected toward the spindle 60 inside the casing 62 and forms the air bearing that supports the spindle 60 as described above flows downward through the small gaps that serve as air passages between the plate portion 601 of the spindle 60 and the air injection portion 621 of the casing 62, between the mounting portion 602 of the spindle 60 and the air injection portion 621, and between the outer surface of the long shaft portion 600 of the spindle 60 and the air injection portion 621, and reaches the gap 6027. The air that constitutes the air bearing can also more reliably discharge grinding water mixed with grinding chips that has entered the gap 6027 from the gap 6027 and more reliably prevent grinding water mixed with grinding chips from entering between the outer surface of the spindle 60 and the inner surface of the cover 65, thereby preventing the spindle 60 from being scraped.

[0039] The above-mentioned intake of air 9 into inlet passage 667 is thought to occur, for example, due to the phenomenon described below. One of the presumed phenomena is that air 9 that was originally present in radial passage 663 is subjected to centrifugal force due to the rotation of spindle 60, flows along radial passage 663 from the center of spindle 60 to the outside, and is released into gap 6027, and new air 9 is then sucked into inlet passage 667 that communicates with radial passage 663. Another presumed phenomenon is the Bernoulli effect. That is, when the exhaust air that constitutes the air bearing is forcefully introduced toward gap 6027, which is narrower than radial path 663, the pressure near the outlet of radial path 663 decreases, causing air 9 in inlet path 667 to be sucked into radial path 663, and further causing air 9 to be sucked into inlet path 667, which communicates with radial path 663, from the opening at the top.

[0040] Similarly, even when the air supply unit 66 includes the radial paths 669 shown in FIG. 4 instead of the radial paths 663, rotation of the spindle 60 causes air 9 to be drawn into the multiple inlet paths 667 through openings in the upper end surface of the longitudinal shaft portion 600 of the inlet paths 667. The air 9 then descends through each inlet path 667 and flows from the center of the spindle 60 to the outside along each radial path 669. As shown in FIG. 4, the outlet 6697 of the radial path 669 is formed such that the outer surface 6024 of the lower mounting portion 602 slopes downward from the outlet 6697 to the outside. Therefore, the air 9 is guided downward along the slope leading to the outlet 6697, and grinding water containing grinding chips that has entered the gap 6027 is discharged from the lower end of the gap 6027 to the outside of the cover 65, thereby cleaning the gap 6027.

[0041] The spindle unit 6 according to the present invention is not limited to the above-described embodiment, and may be embodied in various different forms within the scope of the technical concept thereof. Furthermore, the air cleaning of the gap 6027 is not limited to the example performed during grinding as described above, and may be modified as appropriate within the scope of the effects of the present invention.

[0042] When the grinding mechanism 7 has finished grinding multiple workpieces and is about to stop, for example, when the grinding of the previous workpiece and the grinding of the next workpiece are performed on different days, the control unit (not shown), which is composed of a CPU, storage medium, etc. that controls the grinding mechanism 7, may be programmed in advance to clean the gap 6027 for a predetermined time after grinding of the last workpiece has been completed, and the spindle 60 of the grinding mechanism 7 may be rotated for a predetermined time after grinding has been completed. Alternatively, the worker may manually rotate the spindle 60 to suck air into the entrance path 667 to clean the gap 6027. [Explanation of symbols]

[0043] 7: Grinding mechanism 73: Mount 733: Grinding water distribution channel 74: Grinding wheel 742: Wheel base 743: Annular grinding wheel 746: Injection nozzle 6: Spindle unit 60: Spindle 600: Long shaft portion 601: Plate portion 602: Mounting portion 609: Shaft water flow path 62: Casing 620: Top plate 6204: Pipe joint 625: Water supply pipe 629: Grinding water supply source 621: Air injection part 6213: Air flow path 63: Rotation drive source 632: Rotor 633: Water-cooled radiator 634: Stator 69: Air supply source 65: Cover 66: Air supply section 667: Approach road 668: Lower end of approach road 663: Radiation path 666: Circular approach 669: Radial path

Claims

1. A spindle unit comprising: a spindle having an axial direction in the vertical direction and connected to a mount for mounting a processing tool at its tip; and a casing that surrounds the spindle, injects air from its inner surface to form an air bearing, and rotatably supports the spindle; The mount is connected to a tip of the spindle that protrudes downward from the lower end of the casing, a cover having an upper end attached to the lower surface of the casing and a lower end not in contact with the upper surface of the mount, the cover surrounding the outer surface of the spindle with a gap between the lower surface of the casing and the upper surface of the mount; an air supply unit formed inside the spindle and configured to supply air to the gap by rotation of the spindle; the air supply section includes an inlet passage that opens at an upper portion of the spindle and extends in an axial direction of the spindle, and a radial passage that extends from a lower end of the inlet passage in a radial direction of the spindle, opens at an outer surface of the spindle, and communicates with the gap; A spindle unit in which, as the spindle rotates, air in the radial path is released into the gap by centrifugal force, generating negative pressure in the inlet path, the air is sucked in through the opening at the top of the spindle, the air that has passed through the inlet path and the radial path is released into the gap, and the air passes between the lower end of the cover and the upper surface of the mount, cleaning the gap.

2. 2. The spindle unit according to claim 1, wherein exhaust gas from said air bearing is introduced into said gap.

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