JP2018051646A - Grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding device which automatically adjusts a working condition.SOLUTION: The grinding device is provided, comprising: a chuck table; a grinding unit; a working feed unit; a measurement unit which measures a load on a workpiece held by the chuck table or a load current value of a spindle motor for rotating a spindle; and a control unit which controls each component. The control unit comprises: a control part which controls the working feed unit, the grinding unit, and the chuck table to grind the workpiece under the standard working condition stored in a standard working condition storage part; and an adjustment part which, when a difference between a load measured by the measurement unit and a standard value of the load or a difference between a load current value measured by the measurement part and a standard value of the load current value is larger than a prescribed value, adjusts a working feed speed, a number of revolutions of the spindle or a number of revolutions of the chuck table so that the difference becomes equal to or less than the prescribed value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a grinding apparatus for grinding a workpiece such as a semiconductor wafer.

  A grinding apparatus for grinding (polishing) a plate-like workpiece such as a semiconductor wafer, a package substrate, an optical device substrate, or a ceramic substrate with a grinding wheel or a polishing pad is known.

  For example, a semiconductor wafer is defined by divided division lines called streets in which devices such as IC and LSI are formed on the surface and each device is formed in a lattice shape. Thereafter, the semiconductor wafer is ground from the back side by a grinding device and thinned to a predetermined thickness, and then cut along the streets by the cutting device to be divided into individual chips. The divided chips are widely used by being mounted on various electronic devices such as mobile phones and personal computers.

  A grinding apparatus used for grinding includes a rotatable chuck table that holds a workpiece, a grinding unit that performs grinding by rotating a grinding wheel that holds a grinding wheel, and a work feed that moves the chuck table or the grinding unit. And a unit. The grinding wheel for holding the grinding wheel is mounted on the spindle, and when the spindle motor mounted on the spindle rotates the spindle, the grinding wheel rotates.

  When the grinding wheel is lowered while the grinding wheel and the chuck table are rotated, and the grinding wheel hits the workpiece, the workpiece is ground. In grinding, the rotation speed of the chuck table and grinding wheel, the processing feed rate, etc. are set as processing conditions, and the workpiece is ground according to the processing conditions. Specifically, a load received by the workpiece from the grinding wheel at the time of grinding is determined by the processing conditions and influences the processing result. Therefore, when the processing conditions are set appropriately, a desired processing result can be obtained.

  However, even if the machining conditions are set appropriately, the load applied to the workpiece is appropriate due to individual differences in the workpiece, variations in the surface condition of the grinding wheel, and the way the self-generated blade of the grinding wheel advances. In other cases, an unexpected excessive load may be applied to the workpiece. As a result, the workpiece may be damaged, or the grinding wheel may be clogged and the self-sharpening action of the grinding wheel may be lost. Thereafter, the workpiece may not be ground.

  In Patent Document 1, the load applied to the workpiece during grinding is sequentially measured, and when the grinding load reaches a predetermined threshold value, the grinding means is raised to interrupt the grinding, and further, the load becomes unloaded. There has been disclosed a grinding apparatus that lowers the grinding means and resumes grinding when it becomes short. In this way, it is possible to prevent the grinding wheel from losing its spontaneous blade action without applying an excessive load to the workpiece. However, in this method, since the content of grinding changes due to individual differences of workpieces, the machining results obtained even when machining a plurality of workpieces may not be constant.

JP 2013-226625 A

  Originally, if grinding is performed under appropriate processing conditions, the excessive load as described above is not applied to the workpiece. Moreover, if grinding is repeated on a plurality of workpieces under one machining condition, the same machining result should be obtained. However, as described above, the difference between the workpieces and the way the self-generated blades of the grinding wheel advance affect the load applied to the workpiece and cause variations in the load. Don't be.

  In particular, when grinding a hard substrate such as sapphire or SiC having a high grinding resistance, a package substrate in which a metal post is embedded in a mold resin, or the like, variation in processing results is significant.

  The present invention has been made in view of such a problem, and an object of the present invention is to adjust a rotation speed of a chuck table and a grinding wheel and a processing feed speed from predetermined processing conditions to obtain a desired processing result. It is providing the grinding device which adjusts automatically.

  According to one aspect of the present invention, a worktable held on the chuck table is ground with a chuck table that holds and rotates the work piece, and a grinding wheel held on a grinding wheel attached to the tip of the spindle. A grinding unit that performs the above, a processing feed unit that relatively moves the grinding wheel held by the grinding wheel and the chuck table in the processing feed direction, and a load applied to the workpiece held by the chuck table or A grinding apparatus comprising a measurement unit for measuring a load current value of a spindle motor for rotating a spindle, and a control unit for controlling each component, the control unit serving as a reference processing feed as a reference processing condition A reference machining condition storage unit for storing the speed, the reference spindle rotation speed, and the reference chuck table rotation speed; A control unit for controlling the processing feed unit, the grinding unit, and the chuck table so as to grind the workpiece under the reference processing conditions stored in the condition storage unit, and a load applied to the workpiece A reference value storage unit for storing the reference value of the spindle motor or the load current value of the spindle motor, and the difference between the load measured by the measuring unit and the reference value of the load during grinding, or measured by the measuring unit When the difference between the generated load current value and the reference value of the load current value is greater than a predetermined value, the machining feed rate, the spindle rotation speed, or the chuck table rotation speed is set so that the difference is less than the predetermined value. And an adjusting unit that adjusts the angle.

  According to another aspect of the present invention, a chuck table that holds and rotates a workpiece, and a workpiece that is held on the chuck table by a grinding wheel that is held by a grinding wheel that is attached to the tip of the spindle. A grinding unit that grinds a workpiece, a machining feed unit that relatively moves the grinding wheel held by the grinding wheel and the chuck table in a machining feed direction, and a workpiece held by the chuck table A grinding unit comprising a measuring unit that measures a load applied to the spindle motor or a load current value of a spindle motor that rotates the spindle, and a control unit that controls each component, the control unit as a reference processing condition, Reference machining condition storage unit for storing a reference machining feed rate, a reference spindle rotation speed, and a reference chuck table rotation speed A control unit for controlling the processing feed unit, the grinding unit, and the chuck table so as to grind the workpiece under the reference processing conditions stored in the reference processing condition storage unit; A reference value storage unit for storing a transition of a reference load applied to the spindle or a reference load current value of a spindle motor, a load measured by the measurement unit during grinding, and a load along the transition of the reference load Or the difference between the load current value measured by the measurement unit and the load current value along the transition of the reference load current value is larger than a predetermined value, the difference is less than the predetermined value. And a adjusting unit that adjusts the machining feed rate, the spindle rotation speed, or the chuck table rotation speed.

  Note that in one aspect of the present invention, the control unit derives a correlation for deriving a correlation between the machining feed rate, the spindle rotation speed or the chuck table rotation speed, and the load or the load current value of the spindle motor. A part may be further provided. The control unit may further include a notification unit that issues an alarm when the processing feed rate, the spindle rotation speed, or the chuck table adjustment amount exceeds a threshold value.

  According to the grinding apparatus according to one aspect of the present invention, the measurement unit measures the load applied to the workpiece or the load current value of the spindle motor during grinding, and is a value in accordance with the load or the load current value stored in advance. Whether it can be monitored.

  In the grinding apparatus, the control unit controls each component of the grinding apparatus according to the processing conditions stored in the condition storage unit, and performs grinding. When the load or the like observed by the measurement unit is a value away from the load or the like stored in advance, the adjustment unit works on the control unit to adjust the processing conditions, and the control unit configures each configuration according to the adjusted processing conditions. Control elements. The adjustment is performed so that the load measured by the measurement unit approaches the value of the stored load.

  As a result, even if there is a variation in the load applied to the workpiece due to individual differences in the workpiece or the way the self-generated blade of the grinding wheel advances, machining is performed so that the load applied to the workpiece approaches a predetermined value. Conditions are adjusted. Therefore, when grinding is performed on a plurality of workpieces under the same conditions, the same machining result can be obtained even if the load applied to the workpieces varies.

  Therefore, according to one aspect of the present invention, there is provided a grinding apparatus that automatically adjusts the rotation speed of the chuck table and the grinding wheel and the processing feed speed under predetermined processing conditions so as to obtain a desired processing result.

It is a mimetic diagram explaining composition of a grinding device concerning one mode of the present invention. FIG. 2A is a schematic diagram illustrating a measurement unit that measures the load current of the spindle motor, and FIG. 2B is a schematic diagram illustrating a measurement unit that measures a load applied to the workpiece. . It is a processing condition table which illustrates processing conditions used as a standard. It is a figure which shows an example of transition of the load electric current value of the spindle motor memorize | stored in a reference value memory | storage part, or transition of the load concerning a workpiece.

  Embodiments according to the present invention will be described. A grinding apparatus according to this embodiment will be described with reference to FIG. The grinding apparatus 2 according to the present embodiment is an apparatus that grinds a plate-shaped workpiece such as a semiconductor wafer, a package substrate, an optical device substrate, or a ceramic substrate. For example, a material such as silicon, SiC (silicon carbide), or another semiconductor, or a substrate (wafer) made of a material such as sapphire, glass, or quartz is ground.

  The grinding apparatus 2 according to this embodiment includes a chuck table 8 installed on a disk-like turntable 6, a grinding unit 10 and a grinding unit 10a, a processing feed unit 12, and a measurement unit. Provided on the base 4. The grinding apparatus 2 further includes a control unit 14 that controls each component.

  The grinding device 2 will be described in detail. A column 16 and a column 16a are erected on the rear portion of the base 4, and a grinding unit 10 and a grinding unit 10a are provided on the column 16 and the column 16a, respectively.

  A disk-like turntable 6 is provided on the base 4 so as to be rotatable in a horizontal plane. Three chuck tables 8 are provided on the upper surface of the turn table 6 so as to be 120 degrees apart from each other in the circumferential direction. By rotating the turn table 6, each chuck table 8 has a workpiece loading / unloading area. , And are positioned in the rough grinding region and the finish grinding region, respectively.

  The chuck table 8 has a suction path (not shown) having one end connected to a suction source (not shown) inside, and the other end of the suction path is connected to a holding surface 8 a on the chuck table 8. The holding surface 8a is composed of a porous member, and a negative pressure generated by the suction source is applied to the workpiece such as the semiconductor wafer 1 placed on the holding surface 8a through the porous member, thereby The table 8 sucks and holds the workpiece.

  Each of the grinding unit 10 and the grinding unit 10a includes a grinding wheel 10d held by a grinding wheel 10c that is rotationally driven by a spindle motor 10b. The grinding wheel 10d held by the grinding wheel 10c is configured to be moved up and down by the processing feed unit 12, and comes into contact with the semiconductor wafer 1 held on the chuck table 8 to hold the semiconductor wafer 1 in a predetermined manner. Grind to thickness.

  The portion on the front side of the base 4 is configured to be one step higher than the portion on which the turntable 8 is provided, and the cassette mounting table 18 and the cassette mounting table 22 are fixed to the front end of the base 4. A cassette 20 containing a workpiece such as the semiconductor wafer 1 before grinding is placed on the cassette placing table 18, and a cassette 24 for housing the workpiece after grinding is placed on the cassette placing table 22. Placed.

  A wafer transfer robot 26 is installed on the base 4 adjacent to the cassette mounting table 18 and the cassette mounting table 22. The front portion of the base 4 further includes a positioning table 28 having a plurality of positioning pins, a wafer loading mechanism (loading arm) 30, a wafer unloading mechanism (unloading arm) 32, and cleaning and spinning the ground wafer. And a spinner cleaning device 34 for drying.

  Next, the measurement unit of the grinding apparatus 2 will be described. The measurement unit is, for example, a unit 36 that measures the load current of the spindle motor 10b shown in FIG. When the grinding wheel 10d comes into contact with the workpiece and grinding is started, a resistance to decelerate the rotation of the spindle is generated. Therefore, the spindle motor is increased in current to drive the spindle motor so as to maintain a predetermined rotational speed. The increment is referred to as load current. Therefore, since the load due to grinding is reflected in the load current, the adjustment described later is possible based on the value of the load current.

  Grinding of the workpiece such as the semiconductor wafer 1 is performed while measuring the load current value of the spindle motor 10b with an ammeter 40 connected in series between the power source 38 and the spindle motor 10b. The load current value measured by the ammeter 40 is input to the controller 42, and the controller 42 sends the load current value to the control unit 14.

  The measurement unit is a unit 44 that measures the load applied to the workpiece held on the chuck table 8, for example, as shown in FIG. As shown in FIG. 2B, a load detection unit 44b for detecting a grinding load applied to the workpiece is attached to the upper end side of the support body 44a. The load detection unit 44b is in contact with the lower end of the chuck table 8 in such a manner that the chuck table 8 can be rotated. For example, the load detection units 44b can be attached to three locations at the lower end of the chuck table 8, respectively.

  The load detection unit 44b includes a piezoelectric element, and the piezoelectric element receives a pressure applied to the workpiece by the grinding wheel 10d and generates a voltage. The load detection unit 44b sends this voltage to the controller 46, which converts the voltage into a load value applied to the workpiece and sends the load value to the control unit 14. The controller 46 may send the voltage to the control unit 14, and the control unit 14 may convert the voltage into a load value.

  Next, the control unit 14 provided in the grinding apparatus 2 will be described. The control unit 14 is connected to each component of the grinding apparatus 2 and has a function of controlling each component.

  As shown in FIG. 1, the control unit 14 includes a control unit 14 a that controls each component of the grinding apparatus 2 according to the machining conditions, and a reference machining condition storage unit 14 b that stores a machining condition that serves as a reference. The control unit 14 further receives an adjustment value sent from the measurement unit 14 and gives an instruction to adjust the processing conditions to the control unit 14a, and a reference value storage unit 14d that stores the contents to be a reference of the measurement value. Have.

  The control unit 14a uses the machining conditions stored in the reference machining condition storage unit 14b as a reference, and controls each component of the grinding apparatus 2 according to the machining conditions. Here, in the present embodiment, the processing conditions stored in the reference processing condition storage unit 14b are referred to as reference processing conditions, and are distinguished from the adjusted processing conditions described later. When the grinding progresses and an instruction is received from the adjustment unit 14c, the control unit 14a adjusts the reference processing condition according to the instruction, and controls each component of the grinding device 2 according to the adjusted processing condition.

  First, the control unit 14a of the control unit 14 reads a machining condition serving as a reference from the reference machining condition storage unit 14b. The reference machining conditions are registered in advance in the reference machining condition storage unit 14b by an operator of the machining apparatus 2 or the like. Then, a desired machining condition is selected from the registered machining conditions at the time of grinding, and is read by the control unit 14a.

  The processing conditions are, for example, the processing feed speed of the processing feed unit 12, the rotational speed of the spindle motor 10b, the rotational speed of the chuck table 8, and the finished thickness of the workpiece. The processing conditions are stored for each of the grinding unit 10 used for rough grinding and the grinding unit 10a used for finish grinding. An example of the reference machining conditions stored in the reference machining condition storage unit 14b is shown in FIG. The machining conditions may change during grinding, and in this case, the transition of the machining conditions is stored in the reference machining condition storage unit 14b.

  The adjustment unit 14c of the control unit 14 receives the load applied to the workpiece or the load current value of the spindle motor from the measurement unit, and reads the reference value stored in the reference value storage unit 14d. Then, the value received from the measurement unit is compared with the reference value, and when the difference is larger than a predetermined value, an instruction to adjust the processing conditions so as to reduce the difference is sent to the control unit 14a. The control unit 14a adjusts the machining conditions serving as a reference in accordance with instructions from the adjustment unit 14c, and controls each component of the grinding apparatus 2 according to the adjusted machining conditions.

  The reference value stored in the reference value storage unit 14d is registered in advance by the operator of the grinding apparatus 2 or the like. The reference value is a value determined according to the machining condition, and is a value assumed to be observed by the measurement unit when the workpiece is ground according to the machining condition. The reference value may be changed during grinding. In this case, the reference value storage unit 14d stores a reference transition of the load applied to the workpiece or a reference current transition of the spindle motor load current. . FIG. 4 shows an example of the reference transition 48 stored in the reference value storage unit 14d.

  An example of the transition 48 of the standard is as shown in FIG. The reference value is a value (S0) at the time of non-grinding before the start of grinding (T1), increases from the time (T1) when the grinding wheel comes into contact with the workpiece and grinding starts, and a predetermined processing feed rate is reached. As the grinding proceeds, the steady value (S1) is obtained. The reference value is maintained at the steady value (S1) from the time (T2) when the steady value (S1) is reached to the time (T3) when the workpiece has a predetermined thickness. When the workpiece reaches a predetermined thickness, the machining feed is finished and decreases, the reference value returns to the non-grinding value (S0), and the grinding is finished (T4).

  Then, the adjustment unit 14c compares the measurement value received from the measurement unit with the load or the load current value along the reference transition 48, and if the difference is larger than a predetermined value, the difference Is sent to the control unit 14a to adjust the processing conditions so as to reduce the. Here, the value along the reference transition is the value of the reference transition 48 at the time when the value sent from the measurement unit was measured.

  In addition, the transition of the standard is not limited to the transition of the standard around the time. The transition of the standard is, for example, the transition with the workpiece thickness as the axis, the transition with the remaining planned grinding thickness up to the finished thickness as the axis, or the grinding amount from the start of grinding as the axis It may be a transition. In these cases, the grinding apparatus 2 is further provided with a detection unit that detects the thickness of the workpiece or the grinding amount, and follows the transition of the reference from the detected thickness of the workpiece or the grinding amount. Load value or load current value is derived.

  The grinding performed by the grinding apparatus 2 configured as described above will be described. First, the semiconductor wafer 1 before grinding is accommodated in the cassette 20 as a workpiece.

  The workpiece such as the semiconductor wafer 1 in the cassette 20 is transferred to the positioning table 28 by the wafer transfer robot 26 and then placed on the chuck table 8 positioned in the workpiece transfer / unload area by the wafer transfer mechanism 30. Placed. Next, the turntable 6 rotates, the chuck table 8 is sent to the rough grinding region, and the workpiece is positioned directly below the grinding wheel 10d of the grinding unit 10.

  And the control part 14a of the control unit 14 reads the process conditions used as a reference | standard from the reference | standard process condition memory | storage part 14b, and controls each component of the grinding apparatus 2. FIG. For example, when grinding is performed under condition A among the reference machining conditions shown in FIG. 3, the grinding wheel 10c is rotated at 1000 rpm while the chuck table 8 is rotated at 50 rpm, and the grinding wheel 10d is moved to the workpiece. Contact. The grinding wheel 10d is processed and fed downward at a speed of 0.3 μm / second, and is roughly ground until the workpiece becomes 105 μm.

In the grinding unit 10 for performing rough grinding, for example, a grinding wheel 10d including abrasive grains # 320 to # 400 defined by JIS standard “R6001: Grain size of abrasive for grinding wheel” is used. The mounted grinding wheel 10c is used.

  After the rough grinding, the turntable 6 rotates, the chuck table 8 is sent to the finish grinding region, and the finish grinding by the grinding unit 10a is performed. For example, while rotating the chuck table 8 at 50 rpm, the grinding wheel 10c is rotated at 800 rpm, and the grinding wheel 10d is brought into contact with the workpiece. The grinding wheel 10d is processed and fed downward at a speed of 0.1 μm / second, and is ground until the workpiece reaches 100 μm.

  In the grinding unit 10a that performs finish grinding, for example, a grinding wheel 10d including abrasive grains # 1000 to # 2000 defined by JIS standard “R6001: Grain size of abrasive for grinding wheel” is used. The mounted grinding wheel 10c is used.

  In the present embodiment described above, the grinding unit 10 and the grinding unit 10a are divided into rough grinding and finish grinding, and the workpiece is thinned to a predetermined thickness (finish thickness) by carrying out the grinding step by step. . However, the workpiece may be thinned to a predetermined thickness (finished thickness) by performing grinding with one grinding unit.

  During grinding, the load applied to the workpiece or the load current of the spindle motor is measured by the measurement unit, and the measured value is sent to the adjusting unit 14 c of the control unit 14. The adjustment unit 14c reads the reference value from the reference value storage unit 14d, and compares the value sent from the measurement unit with the reference value.

  If the difference between the two is larger than a predetermined value, the adjustment unit 14c sends an instruction to adjust the processing conditions so as to reduce the difference to the control unit 14a. The control unit 14a reflects the instruction from the adjustment unit 14c in the standard machining conditions, and controls each component of the grinding apparatus 2 based on the adjusted machining conditions.

  When grinding progresses under the adjusted processing conditions, the load applied to the workpiece or the load current value of the spindle motor is brought close to the reference value. If it does in this way, even if it grinds with respect to a several to-be-processed object, each will grind similarly.

  Therefore, even if the load applied to the workpiece varies due to individual differences in the workpiece or the way the self-generated blade of the grinding wheel advances, the processing conditions are adjusted, so the load applied to the workpiece is predetermined. It can be brought close to the value of. Therefore, when grinding is performed on the plurality of workpieces under the same conditions, the machining conditions are adjusted and the same machining result can be obtained even if the load applied to the workpieces varies.

  After the workpiece such as the semiconductor wafer 1 is completely ground, the chuck table 8 is again sent to the workpiece loading / unloading area, and the workpiece is sent to the spinner cleaning device 34 by the wafer carry-out mechanism 32 and cleaned. The The workpiece is stored in the cassette 24 by the wafer transfer robot 26 after the cleaning is completed.

  As described above, the grinding of the workpiece such as the semiconductor wafer 1 is performed by the grinding apparatus 2 according to the present embodiment.

  In addition, this invention is not limited to description of the said embodiment, A various change can be implemented. For example, the control unit 14 of the grinding apparatus 2 further includes a correlation deriving unit that derives a correlation between the machining feed rate, the spindle rotation speed or the chuck table rotation speed, and the load or the load current value of the spindle motor. May be further provided.

  The correlation derivation unit is connected to the control unit 14a and the adjustment unit 14c of the control unit 14, and processing conditions sent from the control unit 14a to each component of the grinding apparatus 2, a measurement value by the measurement unit received by the adjustment unit 14c, Accumulate. Then, the correlation deriving unit analyzes the processing conditions and the measured values to derive a correlation.

  When the correlation between the machining condition and the measured value is clarified by the correlation deriving unit, the adjustment content can be determined with reference to the correlation when the adjusting unit 14c adjusts the machining condition. Then, highly accurate adjustment is possible, and a machining apparatus with less variation in machining results can be realized.

  Further, the control unit 14 of the grinding apparatus 2 according to the present embodiment may further include a notification unit that issues an alarm when the processing feed speed, the spindle rotation speed, or the adjustment amount of the chuck table exceeds a threshold value.

  The notification unit is connected to the adjustment unit 14c of the control unit 14, and monitors the adjustment of the processing conditions by the adjustment unit 14c. When the adjustment of the processing conditions by the adjusting unit 14c becomes an excessive adjustment exceeding a predetermined threshold, an alarm is issued to warn the operator of the apparatus.

  When excessive adjustment is required for the processing conditions, there may be a possibility that a peculiar problem exceeding general variation or the like has occurred in the grinding apparatus or the workpiece. Since such a problem should be dealt with individually by an operator or the like, the notification unit issues a warning and prompts the operator or the like to deal with the problem. When the notification unit issues a warning in this manner, the problem is recognized early and it is possible to cope with it before the problem becomes serious.

  In addition, the structure, method, and the like according to the above-described embodiment can be appropriately modified and implemented without departing from the scope of the object of the present invention.

DESCRIPTION OF SYMBOLS 1 Semiconductor wafer 2 Grinding device 4 Base 6 Turntable 8 Chuck table 8a Holding surface 10, 10a Grinding unit 10b Spindle motor 10c Grinding wheel 10d Grinding wheel 12 Processing feed unit 14 Control unit 14a Control unit 14b Reference processing condition storage unit 14c Adjustment Section 14d Reference value storage section 16, 16a Column 18, 22 Cassette mounting table 20, 24 Cassette 26 Wafer transfer robot 28 Positioning table 30 Wafer loading mechanism (loading arm)
32 Wafer unloading mechanism (unloading arm)
34 Spinner Cleaning Device 36 Unit for Measuring Load Current Value of Spindle Motor 38 Power Supply 40 Ammeter 42 Controller 44 Unit for Measuring Load Applied to Workpiece 44a Support 44b Load Detection Unit 46 Controller 48 Transition of Reference

Claims (4)

A chuck table that holds and rotates a workpiece, a grinding unit that grinds the workpiece held on the chuck table by a grinding wheel held on a grinding wheel attached to the tip of a spindle, and the grinding wheel A processing feed unit that moves the held grinding wheel and the chuck table relative to each other in the processing feed direction, and a load applied to the workpiece held on the chuck table or a load current value of a spindle motor that rotates the spindle A measurement unit for measuring the control unit, and a control unit for controlling each component,
The control unit is
A reference processing condition storage unit that stores a reference processing feed rate, a reference spindle rotation speed, and a reference chuck table rotation speed as reference processing conditions;
A control unit for controlling the processing feed unit, the grinding unit, and the chuck table so as to grind the workpiece under the reference processing conditions stored in the reference processing condition storage unit;
A reference value storage unit for storing a reference value of a load applied to a workpiece or a reference value of a load current value of a spindle motor;
When grinding, the difference between the load measured by the measurement unit and the reference value of the load, or the difference between the load current value measured by the measurement unit and the reference value of the load current value is greater than a predetermined value And a adjusting unit that adjusts the machining feed rate, the spindle rotation speed, or the chuck table rotation speed so that the difference is less than or equal to the predetermined value. A chuck table that holds and rotates a workpiece, a grinding unit that grinds the workpiece held on the chuck table by a grinding wheel held on a grinding wheel attached to the tip of a spindle, and the grinding wheel A processing feed unit that moves the held grinding wheel and the chuck table relative to each other in the processing feed direction, and a load applied to the workpiece held on the chuck table or a load current value of a spindle motor that rotates the spindle A measurement unit for measuring the control unit, and a control unit for controlling each component,
The control unit is
A reference processing condition storage unit that stores a reference processing feed rate, a reference spindle rotation speed, and a reference chuck table rotation speed as reference processing conditions;
A control unit for controlling the processing feed unit, the grinding unit, and the chuck table so as to grind the workpiece under the reference processing conditions stored in the reference processing condition storage unit;
A reference value storage unit for storing the transition of the reference load applied to the workpiece or the transition of the reference load current value of the spindle motor;
During grinding, the difference between the load measured by the measuring unit and the load along the transition of the reference load, or the transition of the load current value measured by the measuring unit and the reference load current value An adjustment unit that adjusts a machining feed rate, a spindle rotation speed, or a chuck table rotation speed so that the difference between the load current value and the load current value is larger than a predetermined value, so that the difference is less than the predetermined value A grinding device characterized by the above.   The control unit further includes a correlation deriving unit for deriving a correlation between the machining feed rate, the rotation speed of the spindle or the rotation speed of the chuck table, and the load or the load current value of the spindle motor. The grinding apparatus according to claim 1 or 2.   4. The control unit according to claim 1, further comprising a notification unit that issues a warning when the machining feed rate, the spindle rotation speed, or the adjustment amount of the chuck table exceeds a threshold value. 5. The grinding apparatus as described.