spindle unit

Abstract

[Problem] Preventing machining fluid containing machining chips from remaining in the gap between the spindle and the cover. [Solution] A spindle unit 6 includes a housing 62, a cover 65, and an air supply unit 66. The housing 62 surrounds a spindle 60 with the vertical direction as its axis and forms an air bearing to support it. A mounting base 73 is connected to the front end of the spindle 60 that protrudes downward from the lower end of the housing 62. The cover 65 surrounds the spindle 60 with a gap 6027 between the lower surface of the housing 62 and the upper surface of the mounting base 73, which is exposed on the outer side of the spindle 60. The air supply unit 66 is formed inside the spindle 60. The air supply unit 66 provides air to the gap 6027 by rotating the main shaft. The air supply unit 66 includes: an inlet passage 667 that opens at the upper part of the main shaft 60 and extends in the axial direction; and a radial passage 663 that extends from the lower end of the inlet passage 667 toward the radial direction of the main shaft 60 and opens on the outer side of the main shaft 60 to communicate with the gap 6027. Air drawn in from the opening at the upper part of the rotating main shaft 60 passes through the inlet passage 667 and the radial passage 663 and is released to the gap 6027 to clean the gap 6027.

Description

[Technical Field]

[0001] This invention relates to a spindle unit. [Previous Technology]

[0002] As disclosed in Patent Document 1, for example, a grinding device that grinds a workpiece held in a work chuck with a grinding stone has an annular grinding stone installed on a mounting base connected to the front end of the spindle, and grinds the workpiece with the grinding stone that rotates with the rotation of the spindle.

[0003] As shown, the spindle unit supporting the spindle in a rotatable manner includes: a housing surrounding an upright spindle; a thrust air bearing and a radial air bearing formed by supplying high-pressure air between the housing and the spindle; and a mounting base connected to the front end of the spindle protruding from the lower part of the housing and for mounting the grinding stone. Furthermore, the spindle unit uses a relatively wide area to construct the thrust air bearing in order to withstand a larger vertical load in the axial direction during the grinding process of the spindle. (Prior Art Documents, Patent Documents)

[0004] Patent Document 1: Japanese Patent Application Publication No. 2017-222003 [Summary of the Invention]

[0005] The problem the invention aims to solve

[0006] The spindle unit is designed to eject exhaust air from the side of the spindle, which forms the thrust air bearing. It also includes a cover to protect this ejection outlet from machining chips.

[0007] However, the following problem exists: machining fluid containing machining chips can enter the gap between the spindle and the cover, and subsequently, the machining chips will solidify on the inner surface of the cover and the outer surface of the spindle due to the drying of the machining fluid, preventing the spindle from rotating. Therefore, the following issue arises: a mechanism must be formed in the spindle unit to prevent machining fluid containing machining chips from remaining in the gap between the spindle and the cover. Means for solving this problem...

[0008] The present invention, which addresses the aforementioned problems, is a spindle unit comprising: a spindle, a mounting base for mounting a tool connected to its front end, and the spindle having a vertical axis; and a housing surrounding the spindle and forming an air bearing by injecting air from its inner side, thereby supporting the spindle for rotatability. The spindle unit is a front end of the housing that protrudes downwards from its lower end and is connected to the mounting base to the spindle. It also comprises: a cover, which has a gap between itself and the outer side of the spindle, allowing the spindle to protrude between the lower surface of the housing and the upper surface of the mounting base; and an air supply section formed inside the spindle, which supplies air to the gap by rotation of the spindle. The air supply section comprises: an inlet passage that opens at the upper part of the spindle and extends in the axial direction of the spindle; and a radial passage that extends radially from the lower end of the inlet passage toward the spindle and opens in the outer side of the spindle, communicating with the gap. Air is drawn in from the opening at the top of the spindle by the rotation of the spindle, and then released into the gap through the inlet and the outlet, thereby cleaning the gap.

[0009] Preferably, the spindle unit of the present invention guides the exhaust gas from the aforementioned air bearing into the aforementioned gap. Effects of the Invention

[0010] The spindle unit of the present invention comprises: a spindle, a mounting base for mounting a tool connected to its front end, and the vertical direction serving as the axial direction; and a housing, which surrounds the spindle and forms an air bearing by spraying air from its inner side, and supports the spindle to be rotatable. The aforementioned spindle unit is a front end of the housing that protrudes downward from the lower end of the housing and is connected to the spindle by the mounting base. It also comprises: a cover, which has a gap between itself and the outer side of the spindle to expose the spindle between the lower surface of the housing and the upper surface of the mounting base; and an air supply section formed inside the spindle, which supplies air to the gap by rotating the spindle. The air supply section comprises: an inlet passage that opens at the upper part of the spindle and extends in the axial direction of the spindle; and a discharge passage that extends from the lower end of the inlet passage toward the radial direction of the spindle and opens at the outer side of the spindle and communicates with the gap. This allows air to be drawn in from the opening at the upper part of the spindle by rotating the spindle, and the air through the inlet passage and the discharge passage is released into the gap to clean the gap. In other words, since air can be sent into the gap between the cover and the outer side of the spindle by rotating the spindle, grinding water mixed with grinding chips that has entered the gap can be discharged from the gap. Furthermore, it can be formed so that grinding chips will not be generated between the outer side of the spindle and the inner side of the cover, thus preventing spindle jamming and other rotational defects.

[0011] The spindle unit of the present invention can introduce the exhaust of the air bearing through the gap between the cover and the outer side of the spindle, so as to more reliably discharge grinding water mixed with grinding chips that has entered the gap from the gap, and thus can be formed to prevent spindle jamming and other rotational defects.

Implementation Method

[0013] Form used to implement the invention

[0014] Figure 1 shows a grinding mechanism 7 for grinding a workpiece such as a semiconductor wafer held in a work chuck (not shown). The grinding mechanism 7 includes the spindle unit 6 of the present invention, a mounting base 73 connected to the front end (lower end) of the spindle 60 constituting the spindle unit 6, and a grinding wheel 74, a tool, mounted on the lower surface of the mounting base 73. Furthermore, the grinding wheel mounted on the lower surface of the mounting base 73 can be, for example, a CMP polishing pad mounted across a platen, a dry polishing pad, or a cutting tool that cuts the workpiece while rotating.

[0015] The grinding wheel 74, which is fixed to the lower surface of the circular plate-shaped mounting base 73 by bolts (not shown), has a wheel base 742 and a plurality of generally rectangular grinding wheel segments arranged in a ring on the bottom surface of the wheel base 742. The grinding wheel segments are formed by fixing diamond abrasive grains with, for example, a resin bond or a ceramic bond. Furthermore, a ring-shaped grinding stone 743 can be formed by the plurality of grinding wheel segments arranged in a ring. Alternatively, a ring-shaped grinding stone without gaps, that is, a continuously arranged grinding stone, can be arranged on the lower surface of the wheel base 742.

[0016] Inside the mounting base 73, a grinding water distribution path 733 is formed, entering from the upper surface and branching radially into a plurality of branches. The grinding water distribution path 733 is connected to the grinding water supply source 629 and serves as a channel for the grinding water. Furthermore, a spray nozzle 746 is formed on the lower surface of the wheel base 742. The spray nozzle 746 has a plurality of openings spaced evenly in the circumferential direction and is connected to the grinding water distribution path 733, primarily spraying grinding water towards the inner surface of the grinding stone 743. The grinding water sprayed from the spray nozzle 746 is supplied to the contact area between the grinding stone 743 and the workpiece (e.g., a semiconductor wafer, not shown), for cleaning and cooling of the contact area.

[0017] The spindle unit 6 includes a spindle 60 and a housing 62. The spindle 60 is connected to a mounting base 73 for mounting the grinding wheel 74 at its front end (lower end) and the vertical direction (Z-axis direction) is used as the axis direction. The housing 62 surrounds the spindle 60 and sprays air from its inner side to form an air bearing to support the spindle 60 so that it can rotate.

[0018] As shown in FIG. 1, the main shaft 60, which is supported by the housing 62 in a non-contact manner, includes: a long shaft portion 600, which is cylindrical and extends in the Z-axis direction; a circular plate-shaped plate portion 601, which is integrally formed with the long shaft portion 600 at the middle position and extends radially outward from the long shaft portion 600; and a circular plate-shaped mounting portion 602, which is integrally extended radially outward from the lower side of the long shaft portion 600 and is mounted on the mounting base 73. A slight gap is formed between the plate portion 601 and the mounting portion 602 and the inner surface of the housing 62.

[0019] As shown in Figure 1, an internal water flow path 609 is formed inside the spindle 60, extending through the Z-axis direction and serving as a channel for grinding water passing through the center of rotation. The internal water flow path 609 is connected to the grinding water distribution path 733 formed within the mounting base 73.

[0020] The top plate 620 of the housing 62 has a central passage for the upper end of the long shaft portion 600 of the spindle 60, and a pipe joint 6204 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 the internal water flow path 609 of the spindle 60. Furthermore, a grinding water supply source 629, consisting of a pump or the like, capable of supplying grinding water (e.g., pure water), is connected to the upper end of the water supply pipe 625. In the case where the machining mechanism of the spindle unit 6 is a grinding mechanism, a grinding fluid supply source replaces the grinding water supply source 629 and is connected to the internal water flow path 609.

[0021] As shown in FIG1, for example, the casing 62, which is formed in the shape of a generally cylindrical shape with a top, forms an air bearing inside which the main shaft 60 is supported in a non-contact manner by the pressure of the air supplied from the air supply source 69, which is composed of a compressor or the like.

[0022] The specific structure of the air bearing described above will be explained. As shown in FIG. 1, the lower end of the housing 62 is provided with an annular plate-shaped air injection section 621 that enters between the plate portion 601 and the mounting portion 602 of the main shaft 60. Slight gaps forming air passages are provided between the plate portion 601 of the main shaft 60 and the air injection section 621 of the housing 62, between the mounting portion 602 of the main shaft 60 and the air injection section 621, and between the outer surface of the long shaft portion 600 of the main shaft 60 and the air injection section 621. A plurality of injection ports (not shown) are formed on the outer surface (upper surface, lower surface, and inner circumferential surface) of the air injection section 621, and each injection port is connected to the air supply source 69 via an air flow path 6213 within the air injection section 621 and an external pipe.

[0023] The high-pressure air supplied from the air supply source 69 shown in Figure 1 is injected through the air flow path 6213 and sprayed from the nozzles of the air injection section 621 onto the outer surface of the spindle 60 with gaps. In this way, the spindle 60 is floated and supported relative to the housing 62 by the high-pressure air. Radial air bearings and thrust air bearings can be formed inside the housing 62, and the outer surface of the spindle 60 is rotatably supported by radial and thrust air bearings in both the radial and axial directions. At this time, because the plate portion 601 and the mounting portion 602 of the spindle 60 are floated and supported by the thrust air bearings over a wider range, the machining load (vertical load) acting on the spindle 60 in the thrust direction (Z-axis direction) is appropriately distributed.

[0024] The rotary drive source 63 that drives the spindle 60 shown in FIG. 1 to rotate can be, for example, a motor having a rotor 632 and a stator 634. The rotor 632 is connected to the upper side of the long shaft portion 600 of the spindle 60, and the stator 634 is disposed on the inner side of the housing 62 outside the rotor 632 and separated from it by a water-cooled radiator 633. A power source (not shown) is connected to the stator 634 to supply predetermined power to the rotary drive source 63. The rotary drive source 63 rotates the rotor 632 by applying voltage to the stator 634, and thus rotates the spindle 60 on which the rotor 632 is mounted. The water-cooled radiator 633 suppresses the heat generation of the rotary drive source 63.

[0025] The front end side (lower end side) of the spindle 60, namely the mounting part 602, protrudes downward from the lower end of the cover 62 as a whole, and the mounting base 73 is connected to the flat lower surface of the mounting part 602.

[0026] The spindle unit 6 includes a cover 65 and an air supply unit 66. The cover 65 has a gap 6027 between itself and the outer side of the spindle 60, that is, between itself and the outer side 6024 of the mounting part 602 in this embodiment, so as to surround the spindle 60 exposed between the lower surface of the air jet part 621, which is the lower surface of the cover 62, and the upper surface of the mounting seat 73 facing each other in the Z-axis direction. The air supply unit 66 is formed inside the spindle 60 and supplies air to the gap 6027 by the rotation of the spindle 60.

[0027] The cover 65 is formed in, for example, a cylindrical shape, and its upper end is connected to the lower surface of the air jet section 621. The gap 6027 formed between the outer side 6024 of the mounting section 602 and the inner side of the cover 65 is a very small size, for example, about a few millimeters.

[0028] The air supply unit 66 has an inlet passage 667 that opens at the upper part of the main shaft 60 and extends in the axial direction (Z-axis direction) of the main shaft 60, and a radial passage 663 that extends from the lower end 668 of the inlet passage 667 in the radial direction of the main shaft 60 and opens on the outer side of the main shaft 60 and communicates with the gap 6027.

[0029] As shown in Figures 1 and 2, the access passages 667, which have a cross-section of, for example, a circular shape, are formed in a plurality of equal intervals in the circumferential direction on the long axis portion 600 of the main shaft 60 (for example, 12 passages in the example shown in Figure 2), and their upper ends are open on the upper end face of the long axis portion 600. The lower end 668 of the access passages 667 is located inside the mounting portion 602. Furthermore, Figure 2 is a cross-sectional view along a1-a2 of the main shaft unit shown in Figure 1.

[0030] The air supply unit 66 may also have an entry passage 666 as shown in FIG3 instead of the entry passage 667. The entry passage 666 is formed in a ring shape around the circumference of the long axis portion 600 of the main shaft 60.

[0031] As shown in Figures 1 and 2, a plurality of radial paths 663, connected to the lower end 668 of the inlet path 667 and extending radially in the radial direction of the main shaft 60 with the center of the long axis portion 600 as the center, each have an outlet 6637 opening on the outer side 6024 of the mounting portion 602. In the example shown in Figures 1 and 2, the shape of the outlet 6637 is circular with the same diameter as the diameter of the radial path 663. For example, the diameter of the radial path 663 is set to be larger than the size of the gap 6027.

[0032] The air supply unit 66 may also be equipped with a radial path 669 as shown in FIG. 4 instead of the radial path 663. A plurality of radial paths 669, which are connected to the lower end 668 of the inlet path 667 and extend radially in the radial direction of the main shaft 60 with the center of the long axis portion 600 as the center, have their own outlets 6697 at the openings on the outer side 6024 of the mounting portion 602. As shown in FIG. 4, the outer side 6024 of the mounting portion 602 below the outlet 6697 is formed to gradually widen from the inside to the outside and downward. Furthermore, the grinding water mixed with grinding chips that enters between the downwardly inclined surface of the outer side 6024 and the inner side of the cover 65 is discharged by the centrifugal force generated by the rotation of the main shaft 60.

[0033] An air intake vent 622 is provided in the area of ​​the top plate 620 of the housing 62 shown in Figure 1, which is slightly off-center and towards the outer periphery. The upper opening of the access path 667 is located near the lower part of the air intake vent 622. Furthermore, although only one air intake vent 622 is formed in the illustrated example, multiple air intake vents 622 may also be formed at equal intervals along the circumference of the top plate 620.

[0034] Hereinafter, the operation of the grinding mechanism 7 when grinding a workpiece such as a semiconductor wafer is performed using the grinding mechanism 7 shown in FIG1 will be described in detail. The worktable (not shown), which holds the workpiece, moves horizontally to below the grinding mechanism 7. Furthermore, the grinding stone 743 of the grinding mechanism 7 is aligned with the workpiece held in the worktable (not shown).

[0035] Next, the grinding mechanism 7 descends via a grinding feed unit (not shown) consisting of a ball screw or motor, and the grinding stone 743, which rotates in a non-contact manner as the spindle 60, supported by an air bearing formed within the housing 62 as previously described, comes into contact with the workpiece to perform grinding. During grinding, since the workpiece, which is held in the work chuck (not shown), rotates, for example, in the same direction as the grinding stone 743, it also rotates, thus allowing the grinding stone 743 to perform grinding of the entire upper surface of the workpiece.

[0036] In the grinding process, the grinding water supply source 629 shown in FIG1 supplies grinding water for cooling the grinding stone 743 to the internal water flow path 609 in the spindle 60. The grinding water supplied to the internal water flow path 609 is sprayed out from each nozzle 746 of the grinding wheel 74 through the grinding water distribution path 733 of the mounting base 73 and reaches the contact area between the grinding stone 743 and the workpiece. The grinding stone 740 and the workpiece can be cooled by this grinding water, and the grinding chips and the grinding water that becomes machining waste liquid are washed away from the upper surface of the workpiece.

[0037] Previously, the following problem had occurred: the grinding water mixed with the aforementioned grinding chips became droplets and entered the gap 6027 between the cover 65 and the outer surface 6024 of the mounting portion 602. Subsequently, the grinding chips dried due to the drying of the grinding water and adhered to the inner surface of the cover 65 and the outer surface of the mounting portion 602 of the spindle 60, making it impossible for the spindle 60 to rotate. However, in the spindle unit 6 of the present invention, air 9 can be drawn into the inlet passage 667 from the openings on the upper end face of the long shaft portion 600 of the plurality of inlet passages 667 by the rotation of the spindle 60. That is, air 9 is drawn into the cover 62 and enters the inlet passage 667 from the air suction port 622 formed on the top plate 620 of the cover 62, which is located near the opening of the inlet passage 667 of the rotating spindle 60 on the upper end face of the long shaft portion 600. Furthermore, the air 9 descends in each inlet path 667 and flows outward from the center of the main shaft 60 along each radial path 663. The inlet path of the air supply section 66 formed on the long axis portion 600 of the main shaft 60 can also be formed as shown in FIG3 into an annular inlet path 666 that circles around the long axis portion 600 of the main shaft 60, and similarly, air 9 can be drawn in from the opening at the upper end of the inlet path 666 by the rotation of the main shaft 60.

[0038] In addition, the gap 6027 can be cleaned by releasing the air 9 through the radiation path 663 shown in FIG1 toward 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 that has been sent into the gap 6027.

[0039] In this way, in the present invention, the spindle unit 6 can send air 9 through the inlet passage 667 and the discharge passage 663 into the gap 6027 between the cover 65 and the outer side of the mounting part 602 of the spindle 60 by rotating the spindle 60. Therefore, grinding water mixed with grinding chips that has entered the gap 6027 can be discharged from the gap 6027. Furthermore, there will be no poor rotation caused by grinding chips adhering to the outer side of the mounting part 602 of the spindle 60 and the inner side of the cover 65, which would result in the spindle 60 getting stuck.

[0040] Furthermore, in this embodiment, the exhaust air forming the air bearing within the housing 62 is introduced into the gap 6027. That is, during the grinding process, the high-pressure air formed inside the housing 62 and ejected towards the spindle 60 to support the air bearing of the spindle 60, as previously described, flows downward into the gap 6027 through the small gaps that form air passages between the plate portion 601 of the spindle 60 and the air injection portion 621 of the housing 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. Furthermore, by using the air that constitutes the air bearing, the grinding water mixed with grinding chips that has entered the gap 6027 can be discharged from the gap 6027 more reliably. Also, it can more reliably prevent the grinding water mixed with grinding chips from entering between the outer side of the spindle 60 and the inner side of the cover 65, thus preventing the spindle 60 from getting stuck.

[0041] The above can be considered as follows: the intake of air 9 into the inlet passage 667 is caused by, for example, the phenomenon described below. One of the hypothetical phenomena is that the air 9 already present in the radial passage 663 is subjected to centrifugal force generated by the rotation of the main shaft 60 and flows outward from the center of the main shaft 60 along the radial passage 663 to the gap 6027, thereby continuously attracting new air 9 to the inlet passage 667 connected to the radial passage 663. Another hypothetical phenomenon is based on the Bernoulli effect. That is, by forcefully introducing the exhaust of air constituting the air bearing in a manner, for example, toward the gap 6027 which is narrower than the radial passage 663, the pressure near the outlet of the radial passage 663 will decrease, thereby attracting air 9 into the radial passage 663, and the air 9 will be further drawn into the inlet passage 667 connected to the radial passage 663 from the upper opening.

[0042] When the air supply unit 66 is equipped with a radial path 669 as shown in FIG. 4 instead of a radial path 663, the air 9 is also drawn into the radial path 667 from the openings of the plurality of inlets 667 on the upper end face of the long shaft portion 600 by the rotation of the main shaft 60. Furthermore, the air 9 descends in each inlet path 667 and flows outward from the center of the main shaft 60 along each radial path 669. As shown in FIG. 4, because the outlet 6697 of the radial path 669 is formed such that the outer surface 6024 of the mounting portion 602 below the outlet 6697 is widened from the inside outward and downward, the air 9 can be guided downward along the inclined surface connected to the outlet 6697, and the grinding water containing grinding chips that has entered the gap 6027 is discharged from the lower end of the gap 6027 outward from the cover 65 to clean the gap 6027.

[0043] The spindle unit 6 of the present invention is not limited to the above-described embodiment, and can of course be implemented in various different forms within the scope of its technical concept. Furthermore, the air cleaning of the gap 6027 is not limited to the example performed during grinding as described above, and can be appropriately modified within the scope where the effects of the present invention can be achieved.

[0044] Alternatively, the grinding mechanism 7 can be configured such that, after grinding multiple workpieces, and when the grinding mechanism 7 stops (e.g., when the dates for grinding the current workpiece and the next workpiece are different), a program is pre-programmed into the control unit (not shown) of the grinding mechanism 7, which is composed of a CPU or memory medium, to allow a predetermined time for cleaning the gap 6027 after grinding the last workpiece, and to cause the spindle 60 of the grinding mechanism 7 to rotate for a predetermined time after grinding. Alternatively, the spindle 60 can be rotated manually by an operator to allow air to be drawn into the inlet 667 for cleaning the gap 6027. [Simplified Explanation of the Diagram]

[0012] FIG1 is a cross-sectional view showing a grinding mechanism equipped with the spindle unit of the present invention. FIG2 is a cross-sectional view a1-a2 of the spindle unit shown in FIG1 when a plurality of entry paths are formed at equal intervals in the circumferential direction of the spindle. FIG3 is a cross-sectional view a1-a2 of the spindle unit shown in FIG1 when the entry paths are in the shape of an annular cylinder in a planar view. FIG4 is a cross-sectional view illustrating a radial path in which the outer side of the mounting portion of the spindle is formed with an opening facing the cover, and the opening is inclined downward from the inside to the outside.

Claims

1. A spindle unit comprising: a spindle, with a mounting base for mounting a tool connected to its front end and oriented vertically as its axial direction; and a housing surrounding the spindle and forming an air bearing by injecting air from its inner side, thereby supporting the spindle for rotatability, the aforementioned spindle unit being a front end of the housing protruding downward from its lower end and connected to the mounting base to the spindle, and comprising: a cylindrical cover, the upper end of which is mounted on the lower surface of the housing, a gap being formed between the lower surface of the housing and the upper surface of the mounting base and the outer side of the spindle, surrounding the outer side of the spindle; and an air supply section formed inside the spindle, supplying air to the gap by rotation of the spindle, the air supply section comprising: an inlet passage opening at the upper part of the spindle and extending in the axial direction of the spindle; and a radial passage extending from the lower end of the inlet passage in the radial direction of the spindle, opening in the outer side of the spindle and communicating with the gap. By rotating the main shaft, the air in the radiation path is released into the gap by centrifugal force, creating a negative pressure in the inlet path. The air is then drawn in from the opening at the top of the main shaft, released into the gap through the inlet path and the radiation path, and further discharged from the lower end of the gap to the outside of the cover, thus cleaning the gap.

2. The spindle unit of claim 1, wherein the aforementioned machining tool is an annular grinding wheel, and the aforementioned machining tool comprises: a grinding stone; an annular wheel base on which the grinding stone is arranged in an annular manner; and a spray nozzle formed on the aforementioned wheel base and spraying grinding water onto the aforementioned grinding stone, the aforementioned mounting base having a grinding water distribution path for allowing the grinding water sprayed from the spray nozzle to pass through, the aforementioned spindle having an internal water flow path extending through the center in the axial direction, the aforementioned internal water flow path being connected to the grinding water distribution path of the mounting base, and the aforementioned air supply unit being annularly disposed outside the internal water flow path.

3. The spindle unit of request item 1 or 2, which directs the exhaust gas from the aforementioned air bearing into the aforementioned gap.

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