JP7693383B2 - Grinding device and method for grinding workpiece - Google Patents

Description

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

The device chip manufacturing process uses a wafer on which devices are formed in multiple areas partitioned by multiple intersecting streets (planned division lines). By dividing this wafer along the streets, multiple device chips, each equipped with a device, are obtained. The device chips are incorporated into various electronic devices such as mobile phones and personal computers.

In recent years, with the miniaturization of electronic devices, there is a demand for thinner device chips. To address this, a process is sometimes carried out in which the wafer before division is ground with a grinding device to thin it. The grinding device is equipped with a chuck table having a holding surface for holding the workpiece, and a grinding unit for grinding the workpiece, and a grinding wheel including a grinding stone is attached to the grinding unit. The grinding device grinds the workpiece by rotating the grinding wheel and bringing the grinding stone into contact with the workpiece.

When grinding a workpiece such as a wafer using a grinding device, the relative positions of the chuck table and grinding unit are adjusted so that the center of the workpiece held by the chuck table overlaps with the trajectory of the grinding wheel. Then, when the grinding wheel is lowered toward the holding surface of the chuck table while the chuck table and grinding wheel are rotated, the bottom surface of the grinding wheel comes into contact with the top surface of the workpiece, grinding the workpiece. This type of grinding method is called in-feed grinding.

On the other hand, a grinding method called creep feed grinding is sometimes used to grind the workpiece. In creep feed grinding, the grinding wheel is positioned outside the workpiece, and the positional relationship between the chuck table and the grinding unit is adjusted so that the bottom surface of the grinding wheel is positioned lower than the top surface of the workpiece. Then, while rotating the grinding wheel, the chuck table is moved along the processing feed direction (horizontal direction) parallel to the holding surface. As a result, the top surface of the workpiece is ground by the grinding wheel, cutting away the side surface of the workpiece in an arc shape (see Patent Document 1).

JP 2005-28550 A

In creep feed grinding, the grinding wheel collides with the side of the workpiece, so the grinding wheel is subjected to a lateral force (lateral load) parallel to the machining feed direction. If a large lateral load acts on the grinding wheel while grinding the workpiece, the grinding wheel may be damaged (broken, etc.).

In addition, when creep feed grinding is performed on a disk-shaped workpiece such as a silicon wafer, the area of the workpiece that comes into contact with the grinding wheel gradually increases as the processing feed progresses, and the magnitude of the lateral load on the grinding wheel changes. This makes it difficult to grind the entire workpiece under the same conditions, and saw marks with irregular patterns (light and dark) tend to remain on the ground surface of the workpiece. As a result, the surface roughness of the workpiece after grinding tends to be non-uniform.

The lateral load acting on the grinding wheel increases as the processing feed rate increases. Therefore, if the processing feed rate is set low to reduce the lateral load acting on the grinding wheel, the grinding wheel is less likely to be damaged and irregular processing marks are less likely to be formed on the ground surface of the workpiece. However, if the processing feed rate is maintained at a low speed, the time required to grind the workpiece increases, and processing efficiency decreases.

The present invention was made in consideration of such problems, and aims to provide a grinding device capable of grinding a workpiece at an appropriate processing feed rate, and a method of grinding a workpiece using the grinding device.

According to one aspect of the present invention, a grinding device for grinding a workpiece includes a chuck table having a holding surface for holding the workpiece, a grinding unit having a spindle and for grinding the workpiece held by the chuck table with a grinding wheel attached to a tip of the spindle, a moving mechanism for relatively moving the chuck table and the grinding unit at a predetermined processing feed speed along a processing feed direction parallel to the holding surface, a processing load measuring unit for measuring a value corresponding to a load applied to the grinding wheel during grinding of the workpiece, and a control unit , wherein the control unit is configured to measure a load corresponding to a load applied to the grinding wheel during grinding of the workpiece in the processing feed direction parallel to the holding surface. and adjusting a positional relationship between the chuck table and the grinding unit so that the workpiece held by the holding surface and the grinding wheel included in the grinding wheel are separated from each other and the lower surface of the grinding wheel is positioned a predetermined distance below the upper surface of the workpiece, and while rotating the grinding wheel, the workpiece and the grinding wheel are moved relatively in the processing feed direction at a predetermined processing feed speed, thereby causing the grinding wheel to grind the workpiece from one end side to the other end side, and the control unit adjusts the processing feed speed in accordance with a value measured by the processing load measuring unit while the workpiece is being ground.

Preferably, the control unit decreases the machining feed rate when the value measured by the machining load measuring unit exceeds an upper limit of the tolerance range. Also, preferably, the control unit increases the machining feed rate when the value measured by the machining load measuring unit is less than a lower limit of the tolerance range.

Also preferably, the moving mechanism includes a ball screw connected to the chuck table and a ball screw motor that rotates the ball screw, the processing load measuring unit measures a current value of the ball screw motor, and the control unit adjusts the processing feed speed in accordance with the current value of the ball screw motor.Also preferably, the grinding unit includes a spindle motor that rotates the spindle, the processing load measuring unit measures a current value of the spindle motor, and the control unit adjusts the processing feed speed in accordance with the current value of the spindle motor.

According to another aspect of the present invention, there is provided a method for grinding a workpiece using a grinding device, the grinding device comprising: a chuck table having a holding surface for holding the workpiece; and a grinding unit having a spindle and for grinding the workpiece held by the chuck table with a grinding wheel attached to the tip of the spindle, the method including a holding step for holding the workpiece with the holding surface; and a grinding wheel for grinding the workpiece held by the chuck table with a grinding wheel attached to the tip of the spindle, the method including a grinding step for holding the workpiece with the holding surface; and a grinding wheel for grinding the workpiece with a grinding wheel such that the workpiece and a grinding wheel are spaced apart from each other in a processing feed direction parallel to the holding surface, and a lower surface of the grinding wheel is fixed to the grinding wheel. The method includes a preparation step of adjusting the positional relationship between the chuck table and the grinding unit so that the workpiece is positioned a predetermined distance below the top surface of the workpiece, and a grinding step of moving the workpiece and the grinding wheel relatively along the processing feed direction at a predetermined processing feed speed while rotating the grinding wheel, and grinding the workpiece from one end side to the other end side with the grinding wheel, in which a value corresponding to the load applied to the grinding wheel during grinding of the workpiece is measured and the processing feed speed is adjusted in accordance with the value.

Preferably, in the grinding step, the processing feed rate is decreased if the value exceeds the upper limit of the tolerance range. Also, preferably, in the grinding step, the processing feed rate is increased if the value is less than the lower limit of the tolerance range.

A grinding device according to one aspect of the present invention includes a processing load measuring unit that measures a value corresponding to the load applied to the grinding wheel during grinding of a workpiece, and a control unit that adjusts the processing feed speed according to the value measured by the processing load measuring unit. This makes it possible to appropriately increase or decrease the processing feed speed according to the load applied to the grinding wheel, and prevents excessive processing load from being applied to the grinding wheel without making the processing feed speed slower than necessary.

FIG. 2 is a partial cross-sectional side view showing the grinding device. FIG. 2A is a side view showing the chuck table and the grinding unit in the preparation step, and FIG. 2B is a side view showing the chuck table and the grinding unit in the grinding step. FIG. 2 is a block diagram showing a control unit. 11 is a flowchart showing a method for adjusting a processing feed rate.

An embodiment of one aspect of the present invention will be described below with reference to the attached drawings. First, an example of the configuration of a grinding device according to this embodiment will be described. FIG. 1 is a partially cross-sectional side view showing a grinding device 2. In FIG. 1, the X-axis direction (machining feed direction, first horizontal direction, front-back direction) and the Y-axis direction (second horizontal direction, left-right direction) are perpendicular to each other. The Z-axis direction (vertical direction, up-down direction, height direction) is perpendicular to the X-axis direction and the Y-axis direction.

The grinding device 2 includes a base 4 that supports or houses each of the components that make up the grinding device 2. A rectangular parallelepiped opening 4a is provided on the upper surface side of the base 4. Inside the opening 4a, a chuck table (holding table) 6 is provided to hold the workpiece 11 that is to be machined by the grinding device 2.

The upper surface of the chuck table 6 is a flat surface that is roughly parallel to the horizontal direction (XY plane direction) and constitutes a holding surface 6a that holds the workpiece 11. The holding surface 6a is connected to a suction source (not shown) such as an ejector via a flow path (not shown) and a valve (not shown) formed inside the chuck table 6.

A moving mechanism (moving unit) 8 that moves the chuck table 6 along the X-axis direction is provided inside the base 4. The moving mechanism 8 includes a ball screw 10 that is connected to the chuck table 6. The ball screw 10 is disposed along the X-axis direction and is screwed into a nut portion (not shown) that is provided on the chuck table 6 or a moving plate (not shown) that supports the chuck table 6. A ball screw motor 12 that rotates the ball screw 10 is connected to an end of the ball screw 10. A pulse motor, for example, is used as the ball screw motor 12.

When the ball screw 10 is rotated at a predetermined rotational speed by the ball screw motor 12, the chuck table 6 moves along the X-axis direction at a machining feed speed that corresponds to the rotational speed of the ball screw 10. As a result, the chuck table 6 and the grinding unit 28 described below move relatively at the predetermined machining feed speed along the machining feed direction parallel to the holding surface 6a.

The chuck table 6 is also connected to a rotational drive source (not shown) such as a motor that rotates the chuck table 6 around a rotational axis (a rotational axis roughly parallel to the Z-axis direction) roughly perpendicular to the holding surface 6a. In other words, the rotational axis of the chuck table 6 is set along a direction perpendicular to the holding surface 6a.

A rectangular parallelepiped support structure 14 is provided behind the chuck table 6 and the moving mechanism 8 (to the right of the paper in FIG. 1). A moving mechanism (moving unit) 16 is provided on the surface side (front side) of the support structure 14.

The moving mechanism 16 includes a pair of guide rails 18 fixed to the front surface side of the support structure 14. The pair of guide rails 18 are arranged along the Z axis direction while being spaced apart from each other in the Y axis direction. In addition, a flat moving plate 20 is attached to the pair of guide rails 18 so as to be slidable along the guide rails 18.

A nut portion 22 is provided on the back side (rear side) of the moving plate 20. A ball screw 24 is provided between the pair of guide rails 18 along the Z-axis direction, and the ball screw 24 is screwed into the nut portion 22. A ball screw motor 26 that rotates the ball screw 24 is connected to the end of the ball screw 24. For example, a pulse motor is used as the ball screw motor 26.

A grinding unit 28 that grinds the workpiece 11 is attached to the surface side (front side) of the moving plate 20. The grinding unit 28 has a hollow, cylindrical support member 30 fixed to the surface side of the moving plate 20. A cylindrical housing 32 is housed in the support member 30. The lower side of the housing 32 is supported by the bottom surface of the support member 30 via a buffer member 34 made of rubber or the like.

The housing 32 contains a cylindrical spindle 36 arranged along the Z-axis direction. The tip (lower end, one end) of the spindle 36 is exposed from the housing 32 and protrudes downward from the underside of the support member 30 through an opening provided in the bottom of the support member 30. A spindle motor 38 that rotates the spindle 36 is connected to the base end (upper end, other end) of the spindle 36.

A disk-shaped mount 40 made of metal or the like is fixed to the tip of the spindle 36. An annular grinding wheel 42 for grinding the workpiece 11 is attached to the underside of the mount 40. For example, the grinding wheel 42 is fixed to the mount 40 by a fastener (not shown) such as a bolt. In this way, the grinding wheel 42 is attached to the tip of the spindle 36.

The grinding wheel 42 is made of a metal such as aluminum or stainless steel and has an annular base 44 formed to have approximately the same diameter as the mount 40. The upper surface of the base 44 is fixed to the lower surface of the mount 40. A plurality of grinding wheels 46 are fixed to the lower surface of the base 44. For example, a plurality of rectangular parallelepiped grinding wheels 46 are arranged in a ring shape at approximately equal intervals along the circumferential direction of the base 44. The grinding wheels 46 are formed by fixing abrasive grains made of diamond, cBN (cubic boron nitride), etc. with a bonding material (bond material) such as a metal bond, a resin bond, or a vitrified bond. However, there are no restrictions on the material, shape, structure, size, etc. of the grinding wheels 46. The number of grinding wheels 46 can also be set arbitrarily.

When the ball screw 24 is rotated at a predetermined rotational speed by the ball screw motor 26, the moving plate 20 moves (raises and lowers) along the guide rail 18 at a speed corresponding to the rotational speed of the ball screw 24. This causes the chuck table 6 and the grinding unit 28 to move relative to each other at a predetermined speed in a direction perpendicular to the holding surface 6a (Z-axis direction).

The grinding wheel 42 rotates around a rotation axis (a rotation axis roughly parallel to the Z-axis direction) roughly perpendicular to the holding surface 6a of the chuck table 6 by the power transmitted from the spindle motor 38 via the spindle 36 and the mount 40. In other words, the rotation axis of the grinding wheel 42 is set along a direction perpendicular to the holding surface 6a.

When the rotating grinding wheel 46 is brought into contact with the top surface of the workpiece 11 held by the chuck table 6, the top surface of the workpiece 11 is scraped off. This causes the workpiece 11 to be ground, resulting in a thinner workpiece 11.

The grinding device 2 also includes a processing load measuring unit that measures a value (load corresponding value) corresponding to the load (processing load) applied to the grinding wheel 42 during grinding of the workpiece 11. FIG. 1 illustrates a processing load measuring unit 48 connected to the moving mechanism 8 and a processing load measuring unit 50 connected to the grinding unit 28.

For example, the machining load measuring unit 48 is an ammeter that measures the current value of the ball screw motor 12, and the machining load measuring unit 50 is an ammeter that measures the current value of the spindle motor 38. Note that the machining load measuring unit 48 may be built into the ball screw motor 12, and the machining load measuring unit 50 may be built into the spindle motor 38.

When the grinding wheel 46 comes into contact with the workpiece 11 while the ball screw motor 12 is rotating the ball screw 10 to move the chuck table 6 along the X-axis direction, a load is applied to the workpiece 11 and the grinding wheel 42. This increases the torque and current value of the ball screw motor 12 required to maintain the moving speed of the chuck table 6. As a result, the current value of the ball screw motor 12 measured by the processing load measurement unit 48 changes.

In addition, if the grinding wheel 46 comes into contact with the workpiece 11 while the spindle 36 is being rotated by the spindle motor 38, a load is applied to the workpiece 11 and the grinding wheel 42. This increases the torque and current value of the spindle motor 38 required to maintain the rotational speed of the spindle 36. As a result, the current value of the spindle motor 38 measured by the processing load measuring unit 50 changes.

As described above, the change in the load applied to the grinding wheel 42 during grinding of the workpiece 11 is reflected in the current values of the ball screw motor 12 and the spindle motor 38. Therefore, the current values measured by the processing load measuring units 48, 50 correspond to the load corresponding value of the grinding wheel 42.

There is no limit to the type of processing load measuring unit mounted on the grinding device 2. For example, the grinding device 2 may have a load measuring device (load cell) that measures the load on the chuck table 6, or a load measuring device (load cell) that measures the load on the spindle 36. In this case, the load value measured by the load measuring device corresponds to the load corresponding value. Also, an ammeter connected to the ball screw motor 26 can be used as the processing load measuring unit.

Each component of the grinding device 2 (chuck table 6, moving mechanism 8, moving mechanism 16, grinding unit 28, processing load measuring units 48, 50, etc.) is connected to a control unit (control unit, control device) 52 that controls the grinding device 2. The control unit 52 generates control signals that control the operation of the components of the grinding device 2, and controls the operation of the grinding device 2.

For example, the control unit 52 is configured by a computer and includes a calculation section that performs calculations necessary for the operation of the grinding device 2, and a storage section that stores various information (data, programs, etc.) used in the operation of the grinding device 2. The calculation section includes a processor such as a CPU (Central Processing Unit). The storage section includes memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

The workpiece 11 is ground by the grinding device 2. For example, the workpiece 11 is a disk-shaped wafer made of a semiconductor such as silicon, and includes a front surface (first surface) 11a and a back surface (second surface) 11b that are generally parallel to each other. The workpiece 11 is divided into a plurality of rectangular regions by a plurality of streets (planned division lines) arranged in a lattice pattern so as to intersect with each other. Devices (not shown), such as ICs (Integrated Circuits), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), and MEMS (Micro Electro Mechanical Systems) devices, are formed on the front surface 11a side of each of the multiple regions divided by the streets.

By dividing the workpiece 11 along the streets, multiple device chips each equipped with a device are obtained. In addition, before dividing the workpiece 11, the back surface 11b side of the workpiece 11 is ground by the grinding device 2 to thin the workpiece 11, thereby obtaining thin device chips.

There are no limitations on the type, material, size, shape, structure, etc. of the workpiece 11. For example, the workpiece 11 may be a disk-shaped wafer (substrate) made of a semiconductor other than silicon (GaAs, InP, GaN, SiC, etc.), glass, ceramics, resin, metal, etc. Furthermore, the workpiece 11 may be a package substrate such as a CSP (Chip Size Package) substrate or a QFN (Quad Flat Non-leaded package) substrate.

In this embodiment, the workpiece 11 is thinned by performing creep feed grinding, in which the chuck table 6 and the grinding wheel 42 are moved relatively along a processing feed direction parallel to the holding surface 6a to grind the workpiece 11. A specific example of a method for grinding a workpiece using the grinding device 2 is described below.

First, the workpiece 11 is held by the holding surface 6a of the chuck table 6 (holding step). For example, the workpiece 11 is placed on the chuck table 6 so that the front surface 11a faces the holding surface 6a and the back surface 11b is exposed upward. When the suction force (negative pressure) of the suction source is applied to the holding surface 6a in this state, the workpiece 11 is sucked and held by the chuck table 6. Note that a protective sheet made of resin or the like that protects the front surface 11a side (device, etc.) of the workpiece 11 may be attached to the front surface 11a side of the workpiece 11. In this case, the workpiece 11 is held by the holding surface 6a of the chuck table 6 via the protective sheet.

Next, the positional relationship between the chuck table 6 and the grinding unit 28 is adjusted (preparation step). Figure 2(A) is a side view showing the chuck table 6 and the grinding unit 28 in the preparation step.

In the preparation step, the positional relationship between the chuck table 6 and the grinding unit 28 is adjusted so that the workpiece 11 and the grinding wheel 46 are separated from each other in the processing feed direction (X-axis direction) parallel to the holding surface 6a, and the lower surface of the grinding wheel 46 is positioned a predetermined distance below the upper surface (rear surface 11b) of the workpiece 11.

Specifically, first, the position of the chuck table 6 in the X-axis direction is adjusted by the movement mechanism 8 (see FIG. 1) so that the workpiece 11 is positioned in front of the grinding wheel 42 (left side of the paper in FIG. 2(A)) without overlapping with the grinding wheel 42. In addition, the position of the grinding unit 28 in the Z-axis direction is adjusted by the movement mechanism 16 (see FIG. 1) so that the bottom surface of the grinding wheel 46 is positioned lower than the top surface of the workpiece 11. The difference ΔH in the height positions (positions in the Z-axis direction) between the top surface of the workpiece 11 and the bottom surface of the grinding wheel 46 at this time corresponds to the target value for the amount of grinding of the workpiece 11 in the grinding step described below (the difference in thickness of the workpiece 11 before and after grinding).

Next, the chuck table 6 and the grinding unit 28 are moved relatively along the processing feed direction (X-axis direction) while rotating the grinding wheel 42, and the workpiece 11 is ground from one end side to the other end side by the grinding wheel 46 (grinding step). Figure 2 (B) is a side view showing the chuck table 6 and the grinding unit 28 in the grinding step.

In the grinding step, the workpiece 11 is ground by creep feed grinding. Specifically, first, the spindle 36 is rotated by the spindle motor 38 (see FIG. 1), thereby rotating the grinding wheel 42 around a rotation axis that is approximately perpendicular to the holding surface 6a of the chuck table 6. The rotation speed of the grinding wheel 42 is set to, for example, 1000 rpm or more and 3000 rpm or less.

Then, while the grinding wheel 42 is rotating and the chuck table 6 is not rotating, the chuck table 6 is moved by the moving mechanism 8 (see FIG. 1). Specifically, the ball screw 10 is rotated at a predetermined rotational speed by the ball screw motor 12, thereby moving the chuck table 6 at a predetermined speed along the X-axis direction. As a result, the chuck table 6 and the grinding wheel 42 move relatively toward each other at a predetermined processing feed speed along the processing feed direction. The processing feed speed (movement speed of the chuck table 6) is set, for example, to 1 mm/s or more and 20 mm/s or less.

When the chuck table 6 moves and one end of the workpiece 11 (the front end in the direction of movement of the workpiece 11, the right end of the paper in FIG. 2B) reaches the trajectory of the grinding wheel 46, the one end of the workpiece 11 is ground off by the grinding wheel 46. The chuck table 6 then moves along the X-axis direction until the other end of the workpiece 11 (the rear end in the direction of movement of the workpiece 11, the left end of the paper in FIG. 2B) is positioned so that it overlaps with the trajectory of the grinding wheel 46. As a result, the workpiece 11 is ground from one end to the other end by the grinding wheel 46, and the entire workpiece 11 is thinned.

In addition, a grinding fluid supply passage (not shown) for supplying liquid (grinding fluid) such as pure water is provided inside or near the grinding unit 28. When the workpiece 11 is ground by the grinding wheel 46, the grinding fluid is supplied to the workpiece 11 and the grinding wheel 46. This cools the workpiece 11 and the grinding wheel 46, and washes away any debris (grinding debris) generated by the grinding process.

As described above, in creep feed grinding, the chuck table 6 moves along the processing feed direction (horizontal direction) parallel to the holding surface 6a, and the grinding wheel 46 collides with the side of the workpiece 11. As a result, the grinding wheel 46 is subjected to a lateral force (lateral load) parallel to the processing feed direction. If a large lateral load acts on the grinding wheel 46 when grinding the workpiece 11, the grinding wheel 46 may be damaged (broken, etc.).

In addition, when creep feed grinding is performed on a disk-shaped workpiece 11 such as a silicon wafer, the area of the workpiece 11 that comes into contact with the grinding wheel 46 gradually increases as the processing feed proceeds, and the magnitude of the lateral load on the grinding wheel 46 changes. This makes it difficult to grind the entire workpiece 11 under the same conditions, and processing marks (saw marks) with irregular patterns (light and dark) tend to remain on the grinding surface (back surface 11b) of the workpiece 11. As a result, the surface roughness of the workpiece 11 after grinding tends to be non-uniform.

The lateral load acting on the workpiece 11 increases as the processing feed rate increases. Therefore, if the processing feed rate is set low to reduce the lateral load acting on the grinding wheel 46, the grinding wheel 46 is less likely to be damaged and irregular processing marks are less likely to be formed on the workpiece 11. However, if the processing feed rate is maintained at a low speed, the time required to grind the workpiece 11 increases, and processing efficiency decreases.

Therefore, in the grinding step, a value (load response value) corresponding to the load applied to the grinding wheel 42 during grinding of the workpiece 11 is measured, and the processing feed speed is adjusted according to the load response value. This allows the processing feed speed to be appropriately increased or decreased according to the load applied to the grinding wheel 42. As a result, it is possible to prevent excessive processing load from being applied to the grinding wheel 42 without making the processing feed speed slower than necessary.

The machining feed rate in the grinding step is controlled by the control unit 52. FIG. 3 is a block diagram showing the control unit 52. In addition to a block showing the functional configuration of the control unit 52, FIG. 3 also shows a block showing the ball screw motor 12 of the movement mechanism 8 and the machining load measurement units 48, 50.

The control unit 52 includes a speed adjustment section 60 that adjusts the machining feed speed, and a storage section 70 that stores information (data, programs, etc.) used by the speed adjustment section 60 to adjust the machining feed speed. A control signal is input from the control unit 52 to the ball screw motor 12 to control the rotational speed of the ball screw 10 (see FIG. 1), thereby adjusting the machining feed speed.

The speed adjustment unit 60 includes a load comparison unit 62 that compares a value (load corresponding value) corresponding to the load applied to the grinding wheel 42 (see FIG. 1, etc.) with a threshold value. The measured values measured by the processing load measurement units 48, 50 are input to the load comparison unit 62 as the load corresponding value.

Specifically, if the processing load measuring unit 48 is an ammeter that measures the current value of the ball screw motor 12, the current value of the ball screw motor 12 is input from the processing load measuring unit 48 to the load comparing unit 62. Also, if the processing load measuring unit 50 is an ammeter that measures the current value of the spindle motor 38 (see FIG. 1), the current value of the spindle motor 38 is input from the processing load measuring unit 50 to the load comparing unit 62. Below, as a representative example, the operation of the control unit 52 when a load corresponding value (current value of the ball screw motor 12) is input from the processing load measuring unit 48 to the load comparing unit 62 will be described.

The storage unit 70 also includes a threshold storage unit 72 that stores thresholds for the load corresponding values. For example, the threshold storage unit 72 stores upper and lower limit values that define the allowable range of the load corresponding values as threshold values. When the current value of the ball screw motor 12 is input from the processing load measuring unit 48 to the load comparing unit 62, the upper and lower limit values of the current value of the ball screw motor 12 are stored as threshold values in the threshold storage unit 72.

When a load corresponding value is input from the processing load measuring unit 48 to the load comparing unit 62, threshold values (upper and lower limit values of the load corresponding value) are read from the threshold memory unit 72 and input to the load comparing unit 62. The load comparing unit 62 then compares the load corresponding value with the threshold value to determine whether the load corresponding value is within the allowable range, exceeds the upper limit of the allowable range, or is less than the lower limit of the allowable range.

The speed adjustment unit 60 also includes a speed determination unit 64 that determines the machining feed speed. The result of the judgment by the load comparison unit 62 is input to the speed determination unit 64, and the speed determination unit 64 determines a machining feed speed suitable for grinding the workpiece 11 based on the judgment result of the load comparison unit 62.

Specifically, the storage unit 70 includes a speed information storage unit 74 that stores information (speed information) used to determine the machining feed speed. For example, the speed information storage unit 74 stores the current machining feed speed and a correction value (increase or decrease value) for the machining feed speed. When the judgment result is input from the load comparison unit 62 to the speed determination unit 64, the speed information is read from the speed information storage unit 74 and input to the speed determination unit 64. Then, the speed determination unit 64 determines the machining feed speed based on the judgment result of the load comparison unit 62 and the speed information.

For example, if it is determined that the load correspondence value exceeds the upper limit of the tolerance range, the speed determination unit 64 sets the value obtained by subtracting the correction value from the current machining feed speed as the changed machining feed speed. This reduces the machining feed speed by the correction value. On the other hand, if it is determined that the load correspondence value is less than the lower limit of the tolerance range, the speed determination unit 64 sets the value obtained by adding the correction value to the current machining feed speed as the changed machining feed speed. This increases the machining feed speed by the correction value.

The correction value (increase or decrease) of the machining feed rate is set appropriately within a range that does not interfere with grinding of the workpiece 11. For example, the correction value of the machining feed rate can be set to between 1/10 and 1/2 of the current machining feed rate. Furthermore, if the load response value is within the allowable range, the current machining feed rate is maintained.

There is no limit to the speed information stored in the speed information storage unit 74. For example, the speed information storage unit 74 may store, as speed information, a table including multiple sets of data sets indicating the possible numerical range of the load corresponding value and the machining feed speed appropriate when the load corresponding value is within that numerical range. In this case, the machining feed speed corresponding to the numerical range to which the measured load corresponding value belongs is set as the changed machining feed speed.

The speed adjustment unit 60 also includes a motor control unit 66 that controls the ball screw motor 12. The machining feed speed determined by the speed determination unit 64 is input to the motor control unit 66. The motor control unit 66 then outputs a control signal to the ball screw motor 12, and controls the rotation speed of the ball screw motor 12 (the rotation speed of the ball screw 10) so that the movement speed of the chuck table 6 (see FIG. 1) matches the machining feed speed determined by the speed determination unit 64.

In this way, the machining feed speed is adjusted according to the load on the grinding wheel 42 (see FIG. 1, etc.). Although the above describes a case where a load corresponding value (current value of the ball screw motor 12) is input from the machining load measuring unit 48 to the speed adjusting unit 60, the machining feed speed is similarly adjusted when a load corresponding value (current value of the spindle motor 38) is input from the machining load measuring unit 50 to the speed adjusting unit 60. In this case, the upper and lower limit values of the current value of the spindle motor 38 are stored as threshold values in the threshold memory unit 72, and the load comparison unit 62 compares the current value of the spindle motor 38 with the threshold value.

Next, a specific example of a method for adjusting the machining feed rate in the grinding step will be described. FIG. 4 is a flowchart showing a method for adjusting the machining feed rate. Below, the procedure for adjusting the machining feed rate will be described mainly with reference to FIG. 3 and FIG. 4.

When grinding the workpiece 11 with the grinding device 2 (see FIG. 1), the holding step and preparation step are first performed as described above. Then, the grinding wheel 42 is rotated while the chuck table 6 and the grinding unit 28 are moved relatively along the processing feed direction (see FIG. 2(B)). This starts grinding the workpiece 11 (grinding step) (step S1).

When grinding of the workpiece 11 starts, the machining load measuring unit also starts measuring the load corresponding value (step S2). For example, the machining load measuring unit 48 measures the current value of the ball screw motor 12. Or, the machining load measuring unit 50 measures the current value of the spindle motor 38. Then, the measured load corresponding value is input to the load comparison section 62 of the control unit 52.

The load comparison unit 62 compares the load corresponding value input from the machining load measurement units 48, 50 with the threshold value stored in the threshold storage unit 72 (step S3). If the load corresponding value is within the allowable range (YES in step S3), the current machining feed speed is determined to be appropriate, and the machining feed speed is maintained (step S4). On the other hand, if the load corresponding value is outside the allowable range (NO in step S3), the current machining feed speed is determined to be inappropriate, and the machining feed speed is changed.

Specifically, if the load response value exceeds the upper limit of the allowable range (YES in step S5), the speed determination unit 64 determines a modified machining feed speed that is smaller than the current machining feed speed. Then, the motor control unit 66 controls the ball screw motor 12 to match the moving speed of the chuck table 6 with the modified machining feed speed. This reduces the machining feed speed (step S6), and the machining load on the grinding wheel 42 (see FIG. 1, etc.) is reduced.

On the other hand, if the load correspondence value is less than the lower limit of the allowable range (NO in step S5), the speed determination unit 64 determines a modified machining feed speed that is greater than the current machining feed speed. Then, the motor control unit 66 controls the ball screw motor 12 to match the movement speed of the chuck table 6 with the modified machining feed speed. This increases the machining feed speed (step S7), and the time required to grind the workpiece 11 is shortened.

After the machining feed rate is adjusted, machining of the workpiece 11 continues (NO in step S8), and the measurement of the load response value and adjustment of the machining feed rate continue. Then, when grinding of the workpiece 11 is completed (YES in step S8), the machining feed is stopped.

Grinding of the workpiece 11 by the grinding device 2 is achieved by controlling the operation of each component of the grinding device 2 (see FIG. 1, etc.) with the control unit 52. Specifically, the memory (storage section 70) of the control unit 52 stores a program that describes a series of operations of each component of the grinding device 2 required to perform the holding step, preparation step, and grinding step in that order. When grinding the workpiece 11, the control unit 52 executes the program and sequentially outputs control signals to each component of the grinding device 2. This controls the operation of the grinding device 2, and the grinding method of the workpiece according to this embodiment is automatically performed.

As described above, the grinding device according to this embodiment includes processing load measuring units 48, 50 that measure a value corresponding to the load applied to the grinding wheel 42 while grinding the workpiece 11, and a control unit 52 that adjusts the processing feed speed according to the value measured by the processing load measuring units 48, 50. This makes it possible to appropriately increase or decrease the processing feed speed according to the load applied to the grinding wheel 42, and prevents excessive processing load from being applied to the grinding wheel 42 without making the processing feed speed slower than necessary.

In addition, in the method for grinding a workpiece according to this embodiment, the number of times creep feed grinding (preparation step and grinding step) is performed can be set appropriately depending on the material of the workpiece 11, the amount of grinding, etc. In other words, the preparation step and grinding step may be performed two or more times. In addition, the number of times (frequency) the processing feed speed is adjusted in the grinding step can also be freely set.

In addition, the structures, methods, etc. according to the above embodiments can be modified as appropriate without departing from the scope of the present invention.

11 Workpiece 11a Surface (first surface)
11b Back side (second side)
2 Grinding device 4 Base 4a Opening 6 Chuck table (holding table)
6a Holding surface 8 Moving mechanism (moving unit)
10 Ball screw 12 Ball screw motor 14 Support structure 16 Movement mechanism (movement unit)
REFERENCE SIGNS LIST 18 Guide rail 20 Moving plate 22 Nut portion 24 Ball screw 26 Ball screw motor 28 Grinding unit 30 Support member 32 Housing 34 Cushioning member 36 Spindle 38 Spindle motor 40 Mount 42 Grinding wheel 44 Base 46 Grinding stone 48, 50 Processing load measuring unit 52 Control unit (control unit, control device)
60 Speed adjustment unit 62 Load comparison unit 64 Speed determination unit 66 Motor control unit 70 Storage unit 72 Threshold storage unit 74 Speed information storage unit

Claims (8)

A grinding device for grinding a workpiece, comprising:
a chuck table having a holding surface for holding the workpiece;
a grinding unit having a spindle and configured to grind the workpiece held by the chuck table with a grinding wheel attached to a tip of the spindle;
a moving mechanism that relatively moves the chuck table and the grinding unit at a predetermined processing feed speed along a processing feed direction parallel to the holding surface;
a processing load measuring unit for measuring a value corresponding to a load applied to the grinding wheel during grinding of the workpiece;
A control unit,
the control unit adjusts the positional relationship between the chuck table and the grinding unit so that the workpiece held on the holding surface and the grinding wheel included in the grinding wheel are separated from each other in a processing feed direction parallel to the holding surface, and so that the lower surface of the grinding wheel is positioned a predetermined distance below the upper surface of the workpiece, and causes the grinding wheel to grind the workpiece from one end side to the other end side by moving the workpiece and the grinding wheel relatively along the processing feed direction at a predetermined processing feed speed while rotating the grinding wheel,
The grinding apparatus is characterized in that the control unit adjusts the processing feed rate in response to a value measured by the processing load measuring unit during grinding of the workpiece . The grinding device according to claim 1, characterized in that the control unit reduces the machining feed rate when the value measured by the machining load measuring unit exceeds an upper limit of the tolerance range. The grinding device according to claim 1 or 2, characterized in that the control unit increases the machining feed rate when the value measured by the machining load measuring unit is below the lower limit of the allowable range. the moving mechanism includes a ball screw connected to the chuck table and a ball screw motor that rotates the ball screw;
The processing load measuring unit measures a current value of the ball screw motor,
4. The grinding apparatus according to claim 1, wherein the control unit adjusts the processing feed speed in accordance with a current value of the ball screw motor. The grinding unit includes a spindle motor that rotates the spindle;
The processing load measuring unit measures a current value of the spindle motor,
4. The grinding apparatus according to claim 1, wherein the control unit adjusts the processing feed speed in accordance with a current value of the spindle motor. A method for grinding a workpiece using a grinding device, comprising the steps of:
the grinding device includes a chuck table having a holding surface for holding the workpiece, and a grinding unit having a spindle and for grinding the workpiece held by the chuck table with a grinding wheel attached to a tip of the spindle;
a holding step of holding the workpiece on the holding surface;
a preparation step of adjusting a positional relationship between the chuck table and the grinding unit so that the workpiece and a grinding wheel included in the grinding wheel are spaced apart from each other in a processing feed direction parallel to the holding surface, and a lower surface of the grinding wheel is positioned a predetermined distance below an upper surface of the workpiece;
a grinding step of relatively moving the workpiece and the grinding wheel along the processing feed direction at a predetermined processing feed speed while rotating the grinding wheel, and grinding the workpiece from one end side to the other end side with the grinding wheel;
The method for grinding a workpiece, wherein the grinding step includes measuring a value corresponding to a load applied to the grinding wheel during grinding of the workpiece, and adjusting the processing feed rate in accordance with the value. The method for grinding a workpiece according to claim 6, characterized in that in the grinding step, the processing feed rate is reduced if the value exceeds an upper limit of the allowable range. The method for grinding a workpiece according to claim 6 or 7, characterized in that in the grinding step, the processing feed rate is increased if the value is less than the lower limit of the allowable range.

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