JPH09150355A - Grinding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently enhance the flatness of a ground surface, even in the case of performing grinding work of a workpiece by a so-called throughfeed method performing work to the workpiece while moving it linearly relating to a grinding wheel. SOLUTION: A grinding machine is disposed vertically relating to a ground surface of a workpiece 1 also constituted by a spindle 4 mounting a grinding wheel 3, spindle feed means 8 lowering down this spindle 4 toward the workpiece 1 based on a prescribed amount of cut and a workpiece feed table 2 making a rotating and/or linear motion of the workpiece 1 in an XY plane orthogonal to a spindle 4a of the spindle 4. Further, a working attitude correction means 31 is provided, which adjusts one after another an angle formed by the spindle 4 and the concerned ground surface and a cutting amount of the grinding wheel relating to the ground surface during advancing of work of the ground surface of the workpiece 1 by the grinding wheel 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinder for surface grinding a work such as a flat plate using a cup-shaped grindstone.

[0002]

2. Description of the Related Art Conventionally, as a device for surface-grinding a work such as a flat plate, a vertical type front grinding machine is known in which a spindle main shaft is provided perpendicular to a surface to be ground of the work. In this vertical type front grinding machine, a grindstone such as a cup-shaped grindstone is mounted on the spindle spindle, while the workpiece is a plane orthogonal to the spindle spindle (hereinafter this plane is referred to as the XY plane).
It is fixed to a feed table that can move inside, and is configured to perform grinding of the surface to be ground while moving the workpiece with respect to the grindstone.

Here, as the feed table for fixing the work, an XY table which is movable in two directions, that is, an X direction and a Y direction which are orthogonal to each other is generally used. However, like a silicon wafer which is a substrate of an integrated circuit, etc. In the case of grinding a circular work, a table in which a rotary table is stacked on a uniaxial table movable in the X direction (hereinafter, this table is referred to as an Xθ table) is used. FIG.
1 (a) shows the movement of the workpiece 100 with respect to the grindstone 101 when an XY table is used, while FIG.
Workpiece 1 for the grindstone 101 when using the θ table
The movement of 00 is shown. Further, when the Xθ table is used, the work is rotating, so that FIG.
As shown in FIG. 7, the machining of the surface to be ground of the work can be completed by simply moving the uniaxial table by the radius of the work 100.

FIG. 12 shows the specific progress of the grinding process in this front grinding machine. That is, the spindle 103 is lowered with the feed table 102 set at a position where the work 100 does not interfere with the grindstone 101, and the desired cutting amount t with respect to the work 100 is set to the grindstone 1.
01 (see FIG. 12A), the feed table 102 is moved in the XY plane, and the surface 104 to be ground 104 is moved.
The grinding process is performed (see the partial diagram (b)). As a result, when the work 100 passes through the grindstone 101, theoretically, the surface 104 to be ground is ground by the set depth of cut (see division (c)).

[0005]

However, in the so-called through-feed type grinding process in which the surface to be ground is processed while moving the work linearly with respect to the grindstone in this way,
Since the contact area between the grindstone and the work changes moment by moment with the change of the position coordinate of the feed table in the Y plane, the processing reaction force received from the work by the grindstone also changes moment by moment. For example, only a part of the grindstone 12 (b) or (d) in which the whetstone is in contact with the workpiece and in the state in FIG. 12 (c) in which the entire surface of the grindstone is in contact with the ground surface of the workpiece, the cutting amount of the grindstone with respect to the work is several μm. Error will occur. Incidentally, such a change in the processing reaction force is not only caused by the change in the contact area between the grindstone and the work, but also the difference in the shape of the surface to be ground of the work before processing and the change in the state of the grindstone over time. Also caused by.

Further, since the grinding process is performed while moving the workpiece with respect to the grindstone, a bending moment acts on the spindle main shaft on which the grindstone is mounted, and the working reaction force causes an unbalanced load on the grindstone. However, if the spindle does not have sufficient rigidity, the attitude of the grindstone with respect to the surface to be ground of the workpiece will change as the position coordinate of the feed table changes. It will change every moment.

Therefore, in the through-feed type grinding process shown in FIG. 11, for this reason, the center of the surface to be ground of the work is slightly expanded, and the surface to be ground is inclined in one direction and ground. Occurred, and it was difficult to increase the flatness of the surface to be ground. In particular, the silicon wafer of the integrated circuit described above has a thickness of 0.5 μm due to its electrical characteristics and the like.
Although a certain degree of flatness is required, it has been extremely difficult to achieve this with a conventional front grinding machine.

On the other hand, as a countermeasure against such a problem, there has been proposed a so-called in-feed type front grinding machine which processes a surface to be ground without changing the positional relationship between the grindstone and the work. As shown in FIG. 13, this in-feed method uses a grindstone 101 having a diameter larger than that of the work 100, and a radius R of the grindstone 101 is superposed on a radius r of the rotating work 100 so that a surface 104 to be ground 104 is formed. Since the workpiece and the grindstone always maintain the same positional relationship in the XY plane, the fluctuation of the processing reaction force acting on the grindstone is small, and the surface to be ground is expected to have high flatness accordingly. be able to.

However, in this infeed method, since a grindstone having a diameter equal to or larger than the work diameter is required, the moment load acting on the spindle is inevitably large and the surface to be ground is inevitably large. In order to increase the flatness of the spindle, it becomes necessary to increase the rigidity of the spindle itself. Further, since the grindstone has a large diameter, it becomes difficult to form the grindstone, and the front grinding machine itself has to be enlarged.

Further, in recent years, the diameter of silicon wafers has been remarkably increased, and currently 8 inch wafers are becoming the mainstream, but in the future, it is desired to support 12 inch wafers. Therefore, it is expected that it will be more and more difficult to form a surface to be ground having a high degree of flatness with this in-feed type front grinding machine.

The present invention has been made in view of the above problems, and an object of the present invention is to grind a work by a through-feed method.
An object of the present invention is to provide a grinding machine capable of sufficiently increasing the flatness of the surface to be ground.

[0012]

In order to achieve the above object, a grinding machine of the present invention is provided with a spindle which is arranged perpendicularly to a surface to be ground of a work and on which a grindstone is mounted, and a predetermined cut. In a grinder comprising spindle feed means for lowering this spindle toward a work based on the amount, and a work feed table for rotating and / or linearly moving the work in an XY plane orthogonal to the main axis of the spindle, It is characterized in that a machining posture correcting means is provided for sequentially adjusting an angle formed by the spindle and the surface to be ground and a cutting amount of the grindstone with respect to the surface to be ground during the progress of processing of the surface to be ground by the grindstone. is there.

According to such a technical means, while the grindstone mounted on the spindle is processing the surface to be ground of the workpiece, the machining posture correcting means sets the angle between the spindle and the surface to be ground and Since the cutting amount of the grindstone to the surface to be ground is adjusted sequentially, when the cutting amount of the grindstone to the surface to be ground changes due to the change in the processing reaction force that acts on the spindle from the work, or the bending moment that acts on the spindle changes. Even when the inclination of the spindle with respect to the surface to be ground changes due to the above, it is possible to perform processing while correcting this, and it is possible to improve the flatness of the surface to be ground.

As a concrete method for controlling the processing attitude correcting means, a processing attitude detecting means provided with a plurality of displacement sensors, axial force sensors and the like during the actual processing of the surface to be ground of the work is performed. There is a method in which the inclination and the change in height of the spindle with respect to the surface to be ground are detected by using the spindle, and the machining posture correcting means is controlled based on the detected value. That is,
This control method is so-called closed loop control, and when the machining attitude correction means is controlled by using the detection signal obtained by the machining attitude detection means, the control result is detected by the machining attitude detection means and the detected signal is used. The processing posture correcting means is controlled again. As a result, the surface to be ground can be processed while the inclination of the spindle relative to the surface to be ground and changes in the cutting amount of the grindstone are constantly corrected.

Further, as another control method of the machining attitude correcting means, the shape of the ground surface of the work that has been experimentally ground is measured and at the same time the coordinate position of the work in the XY plane is determined from the measurement result. There is also a method of creating the correction data of No. 1 and controlling the machining posture correction means by so-called open loop control based on the correction data. The shape of the surface to be ground actually processed represents the change in the inclination of the spindle and the cutting amount of the grindstone during the processing,
This is because the shape of the work surface to be ground has reproducibility as long as the same work is repeatedly ground under the same grinding conditions.

Further, in this latter control method, the load applied from the grindstone to the work during the test machining of the work is measured, and the correction data is created for each coordinate position of the work in the XY plane from the measurement result. You may do it.
As described above, the spindle inclination and the cutting depth of the grindstone fluctuate according to the change in the processing reaction force that acts on the grindstone from the work, so the load that acts on the work from the grindstone, that is, the working force, is measured in advance. By doing
This is because it is possible to predict the inclination of the spindle and the change in the cutting amount of the grindstone to some extent based on the rigidity of the spindle and the work feed table.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The grinding machine of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a front grinding machine according to a first embodiment of the present invention. In the figure, reference numeral 1 is a work to be ground, reference numeral 2 is an XY table as a work feed table to which the work 1 is fixed, reference numeral 3 is a cup grindstone for processing a surface to be ground of the work 1, reference numeral 4 Reference numeral 5 is a spindle on which the cup grindstone 3 is mounted, reference numeral 5 is a motor for rotating the spindle 4a of the spindle 4 at a predetermined number of rotations, and reference numeral 6 is arranged so as to hold the spindle 4 and move up and down with respect to the apparatus column 7. A spindle head, reference numeral 8 is a spindle feed means for moving the spindle head 6 up and down with respect to the apparatus column 7.

First, the XY table 2 is formed by stacking a lower table 11 movable along the X direction (vertical direction of the paper) and an upper table 12 movable along the Y direction (left and right direction of the paper). And each table 1
The linear bearings 1 and 12 are guided in the X direction or the Y direction by the linear bearings 13 arranged in two rows, and a predetermined amount of feed is given by a ball screw 14 arranged between the linear bearings 13. There is.

FIG. 2 shows the details of the linear bearing. The linear bearing 13 is composed of a track base 15 fixed on the bed 10 or the lower table 11 and a slide base 16 that moves along the track base 15. Although not shown in the drawing, one track base 15 is spaced from each other. Two slide bases 16 and 16 are assembled at a distance. Also,
A table attitude correction unit 17 is fixed to the table mounting surface of the slide table 16, and the tables 11 and 12 are fixed to each slide table 16 via the table attitude correction unit 17.

The table posture correction unit 17 is provided on the slide base 1.
Fixed plate 18 fixed to 6 and each table 11, 1
The movable plate 19 fixed to the movable plate 19 is connected to the movable plate 19 by the thin portion 20, and the fixed plate 18 and the movable plate 1 are connected to each other.
9 is a piezoelectric actuator in which a piezoelectric element 21 is sandwiched between the piezoelectric element 21 and the piezoelectric element 21. The thin portion 20 elastically deforms in response to the voltage applied to the piezoelectric element 21, and the movable plate 19 moves slightly above and below the fixed plate 18. It is designed to be displaced. A strain gauge for detecting the elastic deformation amount of the thin portion 20 is attached to the thin portion 20, and the displacement amount of the movable plate 19 with respect to the fixed plate 18 can be detected based on the detection signal of the strain gauge. It is like this. Note that FIG. 2A shows a state where the piezoelectric element is contracted and the thin portion is not elastically deformed, and FIG. 2B shows a state where the piezoelectric element is extended and the thin portion is elastically deformed. Each one is shown.

The slide table 16 is used for each table 1
Since they are arranged at the four corners of 1 and 12, each slide 16
The piezoelectric element 2 of the table posture correction unit 17 attached to the
By appropriately applying a control voltage to the table 1, the heights of the tables 11 and 12 with respect to the bed 10 can be freely adjusted within the range of expansion and contraction of the piezoelectric element 21, and the heights of the tables 11 and 12 can be adjusted with respect to the spindle main shaft 4a. The tables 11 and 12 can be freely tilted. Although it depends on the amount of expansion and contraction of the piezoelectric element 21 and the amount of deformation of the thin portion, the height of the work chucked on the upper table 12 can be increased to several μm by providing the table attitude correction unit 17 as described above.
It is possible to change the inclination of the work with respect to the spindle shaft 4a up to several seconds.

On the other hand, the spindle 4 is an air spindle that supports the rotation of the main shaft 4a by static air pressure.
It is fixed to the spindle head 6 together with the motor 5 via a spindle attitude correction unit 22. As shown in FIGS. 3 and 4, the spindle posture correction unit 22 includes the thin portion 2
Movable ring 24 and fixed ring 25 connected via 3
The movable ring 24 is fixed to the spindle 4 and the fixed ring 25 is fixed to the spindle head 6 while the piezoelectric element 26 is sandwiched between and. The piezoelectric element 26 is a movable ring 24.
Are evenly distributed in four places on the circumference of.

Therefore, in the spindle attitude correction section 22, the inclination of the spindle 4a is arbitrarily changed by applying a control voltage to each of the piezoelectric elements 26 arranged at four locations around the spindle 4. In addition, the spindle 4 can be slightly lowered with respect to the spindle head 6. At that time, the inclination of the spindle 4a that can be changed is about several seconds, and the descending amount of the spindle 4 is about several μm.

A ball screw is used as the spindle feed means 8, and when a screw shaft 28 is rotated by a motor 27 fixed to the apparatus column 7, a ball nut 29 screwed onto the screw shaft 28 is attached. The spindle head 6 and the device column 7 are moved up and down. The vertical movement of the spindle head 6 is guided by the linear bearing 30.

Therefore, the spindle 4 is provided with a raising / lowering amount according to the rotation amount of the motor 27, but in this embodiment, for the purpose of finely controlling the raising / lowering amount of the spindle, the feed of the ball screw described later is performed. The ball nut 29 is fixed to the spindle head via the amount correction unit 31.

As shown in FIG. 5, the feed amount correction unit 31 connects a fixed ring 32 fixed to the ball nut and a movable ring 33 fixed to the spindle head 6 with a thin portion 34, and This is a piezo actuator in which a piezoelectric element 35 is sandwiched between a fixed ring 32 and a movable ring 33, and the movable ring 33 is displaced up and down slightly with respect to the fixed ring 32 depending on the voltage applied to the piezoelectric element 35. It is supposed to do. In addition, in the partial view (a) of FIG. 5, the piezoelectric element 35 is contracted and the movable ring 33 is
In FIG. 6B, the piezoelectric element 35 is extended and the movable ring 33 is displaced.

Therefore, the piezoelectric element 35 of the feed amount correction unit 31
By appropriately adjusting the applied voltage to the piezoelectric element 35, the feed amount given to the spindle by the rotation of the motor 27 is adjusted.
The amount of expansion and contraction can be corrected, and even when the resolution of the motor is low, it is possible to finely adjust the feed amount of about several μm.

On the other hand, the work 1 is fixed to the chuck 36 provided on the XY table 2, and is ground by the cup grindstone 3 while moving in the XY plane. A laser displacement meter 37 as a shape measuring instrument is provided above the XY table and on the side of the cup grindstone, so that the shape of the surface to be ground of the work that has been ground can be measured by this laser displacement meter 37. It has become.

Then, in the front grinding machine of the present embodiment having the above-mentioned structure, the test work of the work 1 is carried out before the start of the full-scale grinding work, and the surface to be ground obtained by the test work is tested. Correction data for controlling the table attitude correction unit 17, the spindle attitude correction unit 22, and the ball screw feed amount correction unit 31 are created based on the shape.
Then, based on this correction data, while the surface to be ground of the work 1 is being ground by the cup grindstone 3, the piezoelectric elements of the table posture correction unit 17, the spindle posture correction unit 22 and the ball screw feed amount correction unit 31 are piezoelectric. The applied voltage to the element is appropriately adjusted, and the cut amount and the contact angle of the cup grindstone 3 with respect to the work 1 are finely adjusted.

FIG. 6 is a block diagram showing a control system for realizing such control. The broken line arrow indicates the signal path in the test machining of the work 1, and the solid line arrow indicates the work 1 based on the created correction data. The signal path when processing is shown.

During the test machining of the workpiece 1, the shape of the surface to be ground, which is ground by the cup grindstone 3, is measured by the laser displacement meter 37, and the shape measurement signal is a calculation unit composed of a microcomputer. 39 is input. Further, the XY table 2 is provided with a table position detection sensor 38 for detecting the movement position thereof, and the position detection signal is also input to the arithmetic unit 39 together with the shape measurement signal. The computing unit 39 associates the shape measurement signal with the position detection signal, and calculates the workpiece 1 in the XY plane.
The correction data is created for each coordinate position, and the correction data is stored in the correction data storage unit 40.

When the main machining of the work 1 is started, the arithmetic unit 39 reads the correction data corresponding to the coordinate position of the work 1 from the correction data storage unit 40 based on the output signal of the table position detection sensor 38. According to the correction data, a control voltage is applied to each of the piezoelectric elements 21, 26 and 35 of the table posture correction unit 17, the spindle posture correction unit 22 and the ball screw feed amount correction unit 31,
Accordingly, the table attitude correction unit 17 corrects the height and inclination of the XY table 2, the spindle attitude correction unit 22 corrects the inclination of the spindle 4, and the ball screw feed amount correction unit 31 corrects the feed amount of the spindle head.

As a result, in the front grinding machine of the present embodiment, the cutting amount and inclination of the cup grindstone with respect to the work are corrected for each coordinate position of the work 1 in the XY plane based on the correction data obtained in the past grinding process. Therefore, the flatness of the surface to be ground of the work 1 can be significantly improved.

Next, a second embodiment of the present invention will be described. In the above-mentioned first embodiment, the work 1 obtained by the test processing
Although the correction data was created from the shape of the surface to be ground, since the cutting amount and the inclination of the cup grindstone 3 change according to the processing reaction force acting on the cup grindstone 3 from the work 1, it acts on the work 1 during grinding. Even when the load is measured and the correction data is created based on the measured value, the control of the table posture correction unit 17, the spindle posture correction unit 22, and the ball screw feed amount correction unit 31 is performed as in the first embodiment. It is possible to do.

Therefore, in this second embodiment, a multi-axis force sensor is provided between the chuck 36 for fixing the work and the XY table, and is perpendicular to the X, Y and XY planes acting on the work during the test processing. The directional load was measured by this multi-axis force sensor. FIG. 7 is a block diagram showing a control system in this embodiment, and the shape measuring instrument 3 of the first embodiment.
The multi-axis force sensor 41 is used instead of the number 7. Since the other configurations are not different from those of the first embodiment, the description thereof will be omitted here.

Next, a third embodiment of the present invention shown in FIG. 8 will be described. In this embodiment, a machining posture detection sensor 42 is provided around the spindle 4a to measure changes in the inclination and height of the spindle 4a during grinding of the work 1 and to immediately correct the table posture based on the measured values. The unit 17, the spindle posture correction unit 22, and the ball screw feed amount correction unit 31 are controlled.

A capacitance type displacement gauge is used as the processing attitude detecting sensor 42, and in order to accurately detect the inclination of the spindle 4a, the processing attitude is detected at at least three places around the spindle 4a. The sensor 42 was attached.

FIG. 9 is a block diagram showing the control system in this embodiment. In this embodiment, unlike the first or second embodiment described above, the correction data is not created in advance prior to the start of the grinding of the workpiece 1, but the detection signal of the processing attitude detection sensor 42 is used as the calculation unit 43. The control voltage is immediately applied to each of the piezoelectric elements 21, 26, and 35 of the table posture correction unit 17, the spindle posture correction unit 22, and the ball screw feed amount correction unit 31 while performing the process. That is, in this embodiment, if the height or inclination of the spindle 4a during the grinding of the workpiece 1 changes even slightly, a control voltage is applied to the piezoelectric element 26 of the spindle attitude correction unit 22, and the spindle 4 itself moves. The fixed posture with respect to the spindle head 6 is changed so as to cancel the change.

As a result, in the front grinding machine of this embodiment, the cutting amount and the inclination of the cup grindstone with respect to the work are immediately corrected based on the actual change in the posture of the spindle spindle 4a during the grinding process. Similar to the first embodiment, it is possible to remarkably improve the flatness of the surface to be ground of the work 1.

Although the XY table 2 is used as the feed table for the work 1 in the above-described respective embodiments, as shown in FIG. 10, the Xθ table 46 in which the rotary table 45 is mounted on the table 44 movable in the X direction. By using, it is possible to grind the work in the same manner as in each embodiment.

[0041]

As described above, according to the grinding machine of the present invention, the amount of cut and the inclination of the grindstone with respect to the surface to be ground are incremented with time as the positional relationship between the grindstone and the workpiece changes during the grinding process. Even when the workpiece is ground by the through-feed method, the grinding can be performed while correcting such a change by the processing posture correction means. It is possible to sufficiently increase the flatness.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a front grinding machine according to a first embodiment of the present invention.

FIG. 2 is a front view and a side view showing a linear bearing and a table attitude correction unit according to the first embodiment.

FIG. 3 is a cross-sectional view showing a spindle attitude correction unit according to the first embodiment.

FIG. 4 is a view on arrow A in FIG.

FIG. 5 is a cross-sectional view showing a ball screw feed amount correction unit according to the first embodiment.

FIG. 6 is a block diagram showing a control system of the grinding machine according to the first embodiment.

FIG. 7 is a block diagram showing a control system of a grinding machine according to a second embodiment.

FIG. 8 is a schematic configuration diagram showing a third embodiment of the grinding machine of the present invention.

FIG. 9 is a block diagram showing a control system of a grinding machine according to a third embodiment.

FIG. 10 is a schematic configuration diagram showing a grinding machine of the present invention using an Xθ table as a work feed table.

FIG. 11 is a schematic view showing a through-feed type grinding method in a front grinding machine.

FIG. 12 is a schematic view showing a processing procedure of a work in a front grinding machine.

FIG. 13 is a schematic view showing an in-feed type grinding method in a front grinding machine.

[Explanation of symbols]

1 ... Workpiece, 2 ... XY table (workpiece feed table), 3 ... Cup grindstone, 4 ... Spindle, 8 ... Spindle feed means, 22 ... Spindle posture correction unit (machining posture correction means)

Claims (7)

[Claims] 1. A spindle, which is arranged perpendicular to a surface to be ground of a work and has a grindstone mounted thereon, and a spindle feed means for lowering the spindle toward the work based on a predetermined cutting amount, A grinder comprising a work feed table for rotating and / or linearly moving a work in an XY plane orthogonal to the spindle main axis, wherein the spindle and the work surface are processed while the work surface of the work is ground by the grindstone. A grinding machine characterized by being provided with a processing attitude correcting means for sequentially adjusting an angle formed by and a cutting amount of a grindstone with respect to a surface to be ground. 2. A processing attitude detecting means for detecting a change in inclination and height of the spindle with respect to the surface to be ground during processing of the surface to be ground of the work by the grindstone is provided, and based on an output signal from the processing attitude detecting means. The grinding machine according to claim 1, characterized in that the machining posture correcting means is controlled by means of a lever. 3. A shape measuring means for measuring the shape of a surface to be ground of a work that has been experimentally ground is provided,
Correction data creating means for creating correction data for each coordinate position of the workpiece in the XY plane from the output signal of the shape measuring means and storing the correction data is provided, and the machining attitude correction is performed based on the output signal from the correction data creating means. The grinding machine according to claim 1, wherein the means is controlled. 4. A machining force detecting means for measuring a load applied from the grindstone to the workpiece during machining of a surface to be ground of the workpiece is provided, and a coordinate position of the workpiece in the XY plane is obtained from an output signal of the machining force detecting means. 2. The grinding machine according to claim 1, further comprising a correction data creating means for creating and storing correction data for each, and controlling the machining attitude correcting means based on an output signal from the correction data creating means. . 5. The machining posture correcting means is a piezo actuator arranged between the work feed table and a linear bearing for linearly guiding the work feed table in the XY plane. Grinder. 6. The grinding machine according to claim 1, wherein the processing posture correcting means is a piezo actuator arranged between the spindle and a spindle head holding the spindle. 7. The grinding machine according to claim 1, wherein the processing attitude correction means is a piezo actuator arranged between a spindle head holding the spindle and the spindle feed means.