Monitoring system and monitoring method for double disc surface grinding apparatus

Abstract

To appropriately determine that a workpiece of a double-disc surface grinding device is in a non-rotating state while achieving space saving of the entire device, suppression of introduction cost, and suppression of labor required for introduction.SOLUTION: A monitoring system S of a double-disc surface grinding device 1 includes a thickness sensor 101 arranged so as to face at least one of both surfaces of a workpiece W and detecting a thickness between the both surfaces during grinding by a pair of grinding wheels 3, and a controller 100 controlling the pair of grinding wheels 3 based on a detection signal of the thickness sensor 101. When a condition satisfied when the reduction amount of the thickness exceeds a predetermined threshold value is defined as a first condition, the controller 100 executes a monitoring process including a first process of determining whether or not the first condition is satisfied during the operation of the pair of grindstones 3, and a second process of suspending the grinding by the pair of grindstones 3 when the first condition is not satisfied before an elapsed time from a start of the determination of the first condition exceeds a predetermined monitoring time.SELECTED DRAWING: Figure 6A

Description

[Technical Field]

[0001] The present disclosure relates to a monitoring system and a monitoring method for a double disc surface grinding machine. [Background technology]

[0002] Patent Document 1 discloses a wafer rotation detection system. This rotation detection system includes a drive roller that rotates the wafer, a slave roller that rotates following the rotation of the wafer, and a dedicated detector that detects the rotation of the slave roller. The detector detects the rotation of the slave roller, and thereby the rotation of the wafer.

[0003] Patent Document 2 discloses a position detection device for a semiconductor substrate on a rotating device. This position detection device includes a rotation detection unit for detecting the rotation state of the rotating device. This rotation detection unit detects the rotation state (e.g., angular velocity, angular acceleration, and angle) of the rotating device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-173193 [Patent Document 2] Special Publication No. 2007-538391 Summary of the Invention [Problem to be solved by the invention]

[0005] A so-called double-disc surface grinding machine is configured to grind both sides of a rotating workpiece with a pair of grinding wheels. In this double-disc surface grinding machine, grinding by the pair of grinding wheels continues even when the workpiece stops rotating, which can lead to damage to the grinding wheels, the workpiece, and ultimately the entire machine.

[0006] In response to this, as disclosed in the above-mentioned Patent Documents 1 and 2, there is known a technique for detecting the rotation of a workpiece such as a wafer. The inventors of the present application have considered detecting the rotation of the workpiece to monitor whether the workpiece has fallen into a state where it is not rotating normally (hereinafter, this will be referred to as a "non-rotating state"). As soon as it is determined that the workpiece is in a non-rotating state, By interrupting grinding with the grindstone, it is possible to prevent the various types of damage described above.

[0007] However, the techniques disclosed in Patent Documents 1 and 2 both require dedicated and separate sensors such as a detection section, a rotation detection unit, etc. This not only requires space to install such sensors, but also tends to increase costs due to the need to install new sensors.

[0008] Furthermore, the techniques disclosed in Patent Documents 1 and 2 require modification work to install sensors on existing double-disc surface grinding machines, which is troublesome and inconvenient when introduced into existing double-disc surface grinding machines.

[0009] The present disclosure has been made in consideration of these points, and its purpose is to appropriately determine whether the workpiece of a double-head surface grinding machine is in a non-rotating state, while achieving space savings for the entire machine, reducing installation costs, and reducing the effort required for installation. [Means for solving the problem]

[0010] A first aspect of the present disclosure relates to a monitoring system for a double-disc surface grinding machine that includes a rotation mechanism that operates to support and rotate a workpiece, and a pair of grinding wheels that are arranged to sandwich the workpiece supported by the rotation mechanism and are driven to grind both sides of the workpiece.

[0011] According to the first aspect, the monitoring system comprises a first sensor arranged to face at least one of the two surfaces and detecting the thickness between the two surfaces by the pair of grinding wheels during grinding with the pair of grinding wheels, and a controller that controls the pair of grinding wheels based on the detection signal of the first sensor, and when the first condition is defined as a condition that is met when the amount of reduction in thickness exceeds a predetermined threshold, the controller executes a monitoring process including a first process of determining whether the first condition is met while the pair of grinding wheels are operating, and a second process of determining that the workpiece is in a non-rotating state and interrupting grinding with the pair of grinding wheels if the first condition is not met before the elapsed time since the start of determining the first condition exceeds a predetermined monitoring time.

[0012] If the workpiece is rotating normally during grinding with the pair of grinding wheels, it is thought that the detection value of the first sensor will gradually decrease (i.e., the amount of thickness reduction will gradually increase).On the other hand, if the workpiece is not rotating, it is thought that the detection value of the first sensor will not change as it normally does.

[0013] Therefore, according to the first aspect, the controller monitors the amount of reduction in the thickness of the workpiece based on the detection value of the first sensor, and determines that the workpiece is in an unrotated state if the amount of reduction does not exceed a predetermined threshold within the monitoring time.

[0014] The controller then suspends grinding by the pair of grinding wheels as soon as it determines that the workpiece is not rotating, thereby preventing damage to the grinding wheels, the workpiece, and ultimately the entire device.

[0015] Furthermore, the monitoring process according to the first aspect can be realized using conventional sensors for measuring dimensions without the need for installing new sensors. Users of double disc surface grinding machines can realize the monitoring process by simply devising a method for processing performed by the controller, without the need for installing new equipment.

[0016] Therefore, according to the first aspect, it is possible to appropriately determine whether the workpiece of the double-head surface grinding machine is in a non-rotating state while achieving space saving for the entire device, reducing the introduction cost, and reducing the effort required for introduction.

[0017] Furthermore, according to a second aspect of the present disclosure, the controller may be configured to control the movement speed of the pair of grinding wheels relative to the workpiece via the pair of grinding wheels so that a plurality of grinding processes, each of which is different for each grinding process, are executed one by one in sequence, and the controller may be configured to be able to individually execute the monitoring process for each grinding process constituting the plurality of grinding processes.

[0018] According to the second aspect, the controller executes a monitoring process for each grinding process. This makes it possible to identify the grinding process in which the workpiece is not rotating. Based on the results of this identification, the user can improve the configuration related to the double disc surface grinding machine and each grinding process performed by the machine.

[0019] Furthermore, according to a third aspect of the present disclosure, when the plurality of grinding processes are switched from one grinding process to another grinding process, the controller may reset the elapsed time to zero and then start the monitoring process.

[0020] According to the third aspect, the controller restarts counting the elapsed time for each grinding process, which allows the monitoring process to be separated for each grinding process, further improving the ease of use of the monitoring process.

[0021] Furthermore, according to a fourth aspect of the present disclosure, the monitoring time may be set to be longer as the movement speed corresponding to each grinding process in the monitoring process becomes slower.

[0022] The slower the cutting speed (= the moving speed) at which the pair of grinding wheels cuts into the workpiece, the more gradually the amount of thickness reduction increases. Therefore, by setting the monitoring time longer as in the fourth aspect to compensate for the gradual increase in the amount of thickness reduction, the monitoring time can be set to be appropriate for each grinding process. This makes it possible to more accurately determine whether the workpiece is in a non-rotating state.

[0023] Furthermore, according to a fifth aspect of the present disclosure, the monitoring system may include a receiving unit connected to the controller and configured to receive operation input from a user, the plurality of grinding processes including a sparkout in which the moving speed is set to zero, and the controller may be configured to individually switch whether or not to execute the monitoring process for each of the grinding processes excluding the sparkout based on the operation input, and the sparkout may be excluded from the targets for which the monitoring process is executed.

[0024] According to the fifth aspect, it is possible to individually select a grinding process to be monitored from among a plurality of grinding processes. This allows for more flexible settings depending on the type of double disc surface grinding machine and workpiece. This improves the usability of the monitoring system.

[0025] Furthermore, it is believed that the thickness does not substantially change during spark-out, so by excluding spark-out from the monitoring process as in the fifth aspect, unnecessary processing can be omitted.

[0026] Furthermore, according to a sixth aspect of the present disclosure, the controller may be configured to change the monitoring time and the predetermined threshold value individually for each of the grinding processes excluding the spark-out process based on the operation input.

[0027] According to the sixth aspect, the monitoring time and the predetermined threshold can be individually changed for each grinding process. This allows for more flexible settings depending on the type of double disc surface grinding machine and workpiece. This improves the usability of the monitoring system.

[0028] Furthermore, according to a seventh aspect of the present disclosure, the first sensor is a contact-type thickness sensor that detects the thickness by coming into contact with the workpiece being ground by the pair of grinding wheels, and the controller executes a sizing process to determine whether the thickness is within a predetermined range based on the detection signal of the first sensor, and the plurality of grinding processes include one or more first-type processes that involve the sizing process and one or more second-type processes that are performed prior to the first-type processes and do not involve the sizing process, and the controller may continue the sizing process during the first-type process even after the first condition is met, and during the second-type process, move the first sensor away from the workpiece as soon as the first condition is met.

[0029] When the contact-type first sensor is used for a long period of time, there is a concern that the contact portion will wear out. When the monitoring process is used, the frequency of contact between the first sensor and the workpiece increases, so this wear becomes an even greater concern.

[0030] In contrast, as in the seventh aspect, in the second type process, the first sensor is moved away from the workpiece as soon as the first condition is met (i.e., as soon as it is determined that the workpiece is rotating normally). This reduces the frequency of contact between the first sensor and the workpiece, and ultimately reduces wear on the first sensor.

[0031] An eighth aspect of the present disclosure relates to a method for monitoring a double-disc surface grinding machine that includes a rotation mechanism that operates to support and rotate a workpiece, and a pair of grinding wheels that are arranged to sandwich the workpiece supported by the rotation mechanism and are driven to grind both sides of the workpiece.

[0032] According to the eighth aspect, the monitoring method uses a first sensor that is positioned facing at least one of the two surfaces and that detects the thickness between the two surfaces by the pair of grinding wheels during grinding with the pair of grinding wheels, and a controller that controls the pair of grinding wheels based on the detection signal of the first sensor, and the controller executes a monitoring process that includes a first process that determines whether the first condition is met while the pair of grinding wheels are in operation, and a second process that determines that the workpiece is in a non-rotating state and interrupts grinding with the pair of grinding wheels if the first condition is not met before the elapsed time since the start of determining the first condition exceeds a predetermined monitoring time.

[0033] According to the eighth aspect, it is possible to appropriately determine whether the workpiece of the double-head surface grinding machine is in a non-rotating state, while realizing space saving for the entire device, reducing the introduction cost, and reducing the effort required for introduction. [Effects of the Invention]

[0034] As described above, according to the present disclosure, it is possible to appropriately determine whether the workpiece of the double-head surface grinding machine is in a non-rotating state, while achieving space savings for the entire device, reducing the introduction cost, and reducing the effort required for introduction. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a perspective view illustrating a double-disc surface grinding machine. [Figure 2] FIG. 2 is a side view illustrating a double-disc surface grinding machine. [Figure 3] FIG. 2 is a front view illustrating a double-disc surface grinding machine. [Figure 4] FIG. 1 is a block diagram illustrating a monitoring system for a double disc surface grinding machine. [Figure 5] 1 is a table illustrating grinding processes performed by a double disc surface grinding machine. [Figure 6A] 10 is a flowchart illustrating a method for monitoring a double disc surface grinding machine. [Figure 6B] 10 is a flowchart illustrating a method for monitoring a double disc surface grinding machine. [Figure 6C] 10 is a flowchart illustrating a method for monitoring a double disc surface grinding machine. [Figure 7] FIG. 10 is a diagram illustrating an example of a display screen on a reception unit. [Figure 8] FIG. 10 is a perspective view illustrating a double disc surface grinding machine according to a second embodiment. [Figure 9] FIG. 10 is a side view illustrating a double disc surface grinding machine according to a second embodiment. [Figure 10] FIG. 10 is a front view illustrating a double disc surface grinding machine according to a second embodiment. [Figure 11] FIG. 10 is a diagram for explaining determination of monitoring processing. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following description is for illustrative purposes only.

[0037] First Embodiment First, a first embodiment of the present disclosure will be described. For simplicity of explanation, the first embodiment will be simply referred to as the "embodiment" hereinafter.

[0038] Fig. 1 is a perspective view illustrating a double-disc surface grinding apparatus 1. Fig. 2 is a side view illustrating the double-disc surface grinding apparatus 1. Fig. 3 is a front view illustrating the double-disc surface grinding apparatus 1. Fig. 4 is a block diagram illustrating a monitoring system S for the double-disc surface grinding apparatus 1.

[0039] As shown in Fig. 1, the double-disc surface grinding machine 1 includes a rotation mechanism 2 and a pair of grinding wheels 3. The rotation mechanism 2 operates to support and rotate a workpiece W. The pair of grinding wheels 3 are disposed so as to sandwich the workpiece W supported by the rotation mechanism 2, and rotate to grind both surfaces of the workpiece W.

[0040] Here, the workpiece W according to this embodiment is a thin plate-shaped workpiece W. Specifically, this workpiece W is a thin circular semiconductor wafer (silicon wafer). However, it is not essential that the workpiece W is a wafer.

[0041] The double-disc surface grinding machine 1 is configured as a double-disc surface grinding machine (particularly a horizontal double-disc surface grinder in the illustrated example) that simultaneously grinds both the front and back surfaces of a thin circular workpiece W using a pair of grinding wheels 3.

[0042] The rotation mechanism 2 is configured to hold the workpiece W while rotating it around a first central axis O1. Specifically, the rotation mechanism 2 has a plurality of outer peripheral rollers 21 and a plurality of rotation roller groups 22.

[0043] The multiple outer peripheral rollers 21 contact the outer peripheral surface of the workpiece W to support the workpiece W in the radial direction. Specifically, the multiple (four in the illustrated example) outer peripheral rollers 21 are arranged at different angular positions along the circumferential direction of the workpiece W.

[0044] The multiple outer peripheral rollers 21 come into contact with the outer peripheral surface of the workpiece W from different angular positions. This contact allows the multiple outer peripheral rollers 21 to restrict displacement of the workpiece W in the radial direction.

[0045] Each outer peripheral roller 21 rotates around a central axis extending parallel to the first central axis O1. Each outer peripheral roller 21 also functions as a driven roller that rotates in response to the rotation of the workpiece W.

[0046] The plurality of rotating roller groups 22 contact both the front and back surfaces of the workpiece W to support the workpiece W in the axial direction. Specifically, the plurality of (three in the illustrated example) rotating roller groups 22 are arranged at different angular positions along the circumferential direction of the workpiece W.

[0047] The multiple rotating roller groups 22 are each arranged along the periphery of the workpiece W. Each rotating roller group 22 has a first rotating roller 22a that contacts the front surface of the workpiece W and a second rotating roller 22b that contacts the back surface of the workpiece W. The first and second rotating rollers 22a, 22b clamp the workpiece W in the axial direction. By clamping the workpiece W, the multiple rotating roller groups 22 can restrict displacement of the workpiece W in the axial direction.

[0048] Each of the rotating roller groups 22 rotates around a central axis extending perpendicular to the first central axis O1. Some of the rotating roller groups 22 (two in this embodiment) are connected to a workpiece driving mechanism 23 (shown only in FIG. 4).

[0049] The work driving mechanism 23 rotates the rotating roller groups 22 connected to the work driving mechanism 23 around their respective central axes. As a result, the rotating roller groups 22 connected to the work driving mechanism 23 also function as driving rollers that rotate the workpiece W. In addition, the remaining rotating roller groups 22 that are not connected to the work driving mechanism 23 also function as driven rollers that rotate in response to the rotation of the workpiece W.

[0050] The work driving mechanism 23 may be connected to all of the plurality of rotating roller groups 22, or may be connected to one or more of the plurality of outer peripheral rollers 21 in addition to or instead of the rotating roller group 22.

[0051] As shown in Figures 2 and 3, the pair of grinding wheels 3 are configured to rotate around a second central axis O2 that is eccentric from the first central axis O1, thereby simultaneously grinding both sides of the workpiece W held by the rotation mechanism 2.

[0052] Specifically, the pair of grinding wheels 3 includes a first grinding wheel 31 and a second grinding wheel 32 that faces the first grinding wheel across the workpiece W. The first and second grinding wheels 31 and 32 are each a cylindrical cup-shaped grinding wheel with a bottom. The first and second grinding wheels 31 and 32 are each constructed by arranging grinding wheels in a circle on a flange-shaped base material.

[0053] The first and second grinding wheels 31, 32 are arranged with their openings facing each other across the workpiece W. The first and second grinding wheels 31, 32 are arranged coaxially with each other.

[0054] More specifically, the first and second grindstones 31 and 32 are arranged such that the central axes of the respective grindstones, when considered as cylinders, coincide with a second central axis O2 extending parallel to the first central axis O1.

[0055] The first and second grinding wheels 31, 32 are connected to a grinding wheel drive mechanism 4 (shown only in Figure 4) that is configured to rotate the first and second grinding wheels 31, 32 and move the first and second grinding wheels 31, 32 relative to the workpiece W.

[0056] The grindstone driving mechanism 4 rotates the first and second grindstones 31, 32 around the second central axis O2. The grindstone driving mechanism 4 also moves the first and second grindstones 31, 32 in the axial direction along the second central axis O2. When the grindstone driving mechanism 4 moves the first and second grindstones 31, 32 in the axial direction, the pair of grindstones 3 and the workpiece W move relatively toward or away from each other.

[0057] 2 and 3, the diameter of each of the first and second grinding wheels 31, 32 is slightly larger than the radius of the workpiece W. In other words, the workpiece W is laid out so that the center of rotation (first central axis O1) is located inside the periphery of the cup-shaped first and second grinding wheels 31, 32.

[0058] 1 and 4, the double disc surface grinding machine 1 also includes a thickness sensor 101, a controller 100, a timer 102, a receiving unit 103, and an alarm unit 104. As shown in FIG. 4, these elements are also used in and constitute a monitoring system S for the double disc surface grinding machine 1. The thickness sensor 101 is an example of a "first sensor" in this embodiment.

[0059] The thickness sensor 101 is disposed so as to face at least one of the two surfaces of the workpiece W, and is configured to detect the thickness D between the two surfaces during grinding by the pair of grinding wheels 3 (see FIG. 3).

[0060] 2, when the workpiece W is viewed in plan view (when the workpiece W is viewed along the first central axis O1), the portion of the workpiece W ground by the pair of grinding wheels 3 is offset from the portion where the thickness D is detected by the thickness sensor 101. Therefore, the effect of grinding the workpiece W by the pair of grinding wheels 3 (changes in the thickness D) is reflected in the detection result of the thickness sensor 101 as the workpiece W rotates. In other words, when the workpiece W is not rotating, the thickness D detected by the thickness sensor 101 remains approximately constant.

[0061] The thickness sensor 101 according to this embodiment is a measuring device for in-process sizing. That is, the thickness sensor 101 is configured as a sizing device for managing each grinding process performed by the pair of grinding wheels 3. The thickness sensor 101 can be called a dimension measuring device for the workpiece W.

[0062] Specifically, the thickness sensor 101 is a contact-type thickness sensor that detects the thickness D of the workpiece W by coming into contact with the workpiece W while it is being ground by the pair of grinding wheels 3. More specifically, the thickness sensor 101 has a first probe 101a that comes into contact with the front surface of the workpiece W and a second probe 101b that comes into contact with the back surface of the workpiece W.

[0063] The controller 100 is configured to control the pair of grinding wheels 3 based on the detection signal of the thickness sensor 101. Specifically, the controller 100 controls the rotation and movement of the pair of grinding wheels 3. More specifically, the controller 100 controls the rotation speed and movement speed of the pair of grinding wheels 3.

[0064] Here, "rotation" refers to rotation around the second central axis O2, and "movement" refers to movement along the second central axis O2.

[0065] Specifically, the controller 100 according to this embodiment has a CPU, a memory, and an input / output bus, and is configured by, for example, a CNC device. The controller 100 is electrically connected to the thickness sensor 101, the timer 102, the reception unit 103, the notification unit 104, the workpiece driving mechanism 23, and the grinding wheel driving mechanism 4 by wire or wirelessly.

[0066] The timer 102 counts up the elapsed time from the start of the determination of the first condition in the monitoring process described below. This count is reset to zero as appropriate as the grinding process progresses.

[0067] The reception unit 103 is configured to receive operation inputs from a user. In this embodiment, the reception unit 103 is a touch panel.

[0068] In the monitoring process described below, when the workpiece W is not rotating (in a non-rotating state) despite the rotation mechanism 2, particularly the workpiece drive mechanism 23, being in operation, the notification unit 104 notifies the user of this. The notification unit 104 may be a device that can make a sound, such as a buzzer, or may be a device that can be seen by the user, such as a warning lamp.

[0069] The controller 100 controls the grinding wheel driving mechanism 4 to control the moving speed of the pair of grinding wheels 3 relative to the workpiece W. This allows a plurality of grinding processes to be executed one by one in order.

[0070] Fig. 5 shows examples of the grinding processes executed by the double disc surface grinding machine 1. As shown in the figure, the multiple grinding processes are configured so that the movement speed differs for each grinding process. In this embodiment, the total number of the multiple grinding processes is "N (N is a natural number)".

[0071] 5, the multiple grinding processes are performed in chronological order: rough grinding, multiple semi-finish grindings, finish grinding, and spark-out. In this embodiment, for convenience, the multiple grinding processes include spark-out, in which the moving speed is set to zero, but this is not essential. As an example, in this embodiment, the total number of multiple semi-finish grindings is set to "M (M is a natural number less than N)."

[0072] As shown in FIG. 5, the cutting speed (the moving speed described above) of the pair of grinding wheels relative to the workpiece W gradually slows down in chronological order and becomes zero at the spark-out.

[0073] Between grinding processes, the rotation speed of the workpiece W by the workpiece driving mechanism 23 may be varied, the rotation speeds of the first and second grinding wheels 31, 32 may be varied, or the flow rate of the coolant may be varied.

[0074] The controller 100 executes sizing processing based on the detection signal of the thickness sensor 101. The sizing processing is processing to determine whether the thickness D of the workpiece W is within a predetermined range. This sizing processing is executed in one or more of the plurality of grinding processes.

[0075] More specifically, when the workpiece W is a semiconductor wafer as shown in the example, the workpiece W is hard and the execution time of each grinding process is long. On the other hand, in order to execute the sizing process, it is necessary to bring the thickness sensor 101 into contact with the workpiece W.

[0076] Therefore, in order to suppress wear of the first and second probes 101a and 101b, the sizing process is performed in a part of the grinding processes (particularly in the latter grinding processes).

[0077] That is, as shown in FIG. 5, the multiple grinding processes include one or more first-type processes that involve sizing processing, and one or more second-type processes that are performed prior to the first-type processes and do not involve sizing processing.

[0078] In the illustrated example, the second type process includes rough grinding and No. 1 to No. M-2 semi-finish grinding. In these grinding processes, sizing is not performed (sizing: absent). On the other hand, the first type process includes No. M-1 to No. M semi-finish grinding, finish grinding, and spark-out. In these grinding processes, sizing is performed (sizing: present).

[0079] In the above embodiment, wear and position changes of the outer peripheral rollers 21 and the rotating roller groups 22 constituting the rotation mechanism 2, as well as changes in the thickness D of the workpiece W, can cause problems in supporting the workpiece W with the rotation mechanism 2, potentially resulting in the workpiece W falling into a non-rotating state. If the workpiece W falls into a non-rotating state, this can be inconvenient as it can lead to damage to the pair of grinding wheels 3, the workpiece W, and ultimately the entire double disc surface grinding device 1.

[0080] Specifically, the outer periphery of the workpiece W, which is a semiconductor wafer, is gripped by a plurality of outer periphery rollers 21, and both sides of the workpiece W are sandwiched between a group of rotating rollers 22 and rotated, but due to wear of these rollers, changes in gripping force, etc., it is possible that the workpiece W itself will spin freely and be unable to rotate, even though the group of rotating rollers 22 is rotating. When the rotation of the workpiece W stops, the outer periphery rollers 21 that grip the outer periphery also stop, but because there is no way to directly detect the rotation of the outer periphery rollers 21 and the workpiece W, the grinding process continues even though the rotation of the workpiece W has stopped.

[0081] In response to this, the inventors of the present application have come up with a new monitoring process that makes use of an existing or new thickness sensor 101, thereby solving the above-mentioned problem. This monitoring process is a process that is executed by the controller 100.

[0082] Here, the condition that is met when the amount of decrease in thickness D detected by the thickness sensor 101 exceeds a predetermined threshold value is defined as the first condition. The situation in which this first condition is met corresponds to a situation in which both surfaces of the workpiece W are being ground by the pair of grinding wheels 3 while the workpiece W is rotating.

[0083] On the other hand, a situation in which the first condition is not satisfied corresponds to a situation in which the workpiece W is in an unrotated state even though both surfaces of the workpiece W are being ground by the pair of grinding wheels 3. Therefore, the determination of whether the first condition is satisfied can be used to determine whether the workpiece W is in an unrotated state.

[0084] Specifically, the monitoring process according to this embodiment includes a first process and a second process. The first process is a process for determining whether a first condition is met while the pair of grinding wheels 3 are in operation. The second process is a process for determining that the workpiece W is in a non-rotating state and suspending grinding by the pair of grinding wheels 3 if the first condition is not met before the elapsed time from when the determination of the first condition started exceeds a predetermined monitoring time.

[0085] In this embodiment, the controller 100 is configured to be able to individually execute monitoring processing for each grinding process that constitutes a plurality of grinding processes. The monitoring processing is executed or not executed for each process.

[0086] The monitoring process for each grinding process can be switched on and off via the reception unit 103. That is, as shown in Fig. 7, the controller 100 can individually switch whether or not to execute the monitoring process for each grinding process except for spark-out, based on an operation input received by the reception unit 103.

[0087] Specifically, the reception unit 103 as a touch panel is provided with a first touch button 103a and a second touch button 103b for each grinding process.

[0088] The first touch button 103a can be used to switch between executing (ON) and not executing (OFF) the monitoring process for each grinding process. In the illustrated example, "OFF" is selected for rough grinding and the first semi-finish grinding, and "ON" is selected for the second semi-finish grinding to the Mth semi-finish grinding and finish grinding.

[0089] Spark Out is not included in the selection targets of the first touch button 103a, that is, Spark Out is excluded from the execution targets of the monitoring process in this embodiment.

[0090] The second touch button 103b can display a setting screen for the monitoring time and threshold for each grinding process. The controller 100 according to this embodiment can change the monitoring time and threshold for each grinding process, excluding spark-out, based on the operation input received by the receiving unit 103.

[0091] A specific example of the monitoring process will be described below with reference to the drawings. Figures 6A, 6B, and 6C are flowcharts illustrating an example of a method for monitoring the double disc surface grinding machine 1.

[0092] First, prior to step S11 in Fig. 6A, it is assumed that one grinding process (the (n-1)th grinding process) is switched to another grinding process (the nth grinding process) among the total N grinding processes illustrated in Fig. 5. The "nth grinding process" here corresponds to the grinding process that is set to execute the monitoring process.

[0093] Then, in step S11, the controller 100 starts the n-th grinding process (n-th grinding process) out of the total N grinding processes illustrated in FIG.

[0094] The controller 100 controls the workpiece drive mechanism 23, the grinding wheel drive mechanism 4, a coolant supply mechanism (not shown), etc. so as to realize a moving speed etc. corresponding to the started grinding process. The pair of grinding wheels 3 cut into the workpiece W at a predetermined moving speed.

[0095] In the following step S12, the controller 100 reads the monitoring time and the predetermined threshold. Hereinafter, the monitoring time and the predetermined threshold corresponding to the nth grinding process will be referred to as the "nth monitoring time" and the "nth threshold," respectively. The nth monitoring time is set to be at least shorter than the execution time of the nth grinding process.

[0096] As described with reference to FIG. 7, the controller 100 may change the n-th monitoring time and threshold value individually for each grinding process except for spark-out, based on the operation input received by the receiving unit 103.

[0097] Alternatively, as shown in FIG. 5, the controller 100 may read pre-set setting information to set the n-th monitoring time and threshold value individually for each grinding process.

[0098] When the latter setting information is used, the nth monitoring time is set to be longer as the moving speed corresponding to each grinding process becomes slower (i.e., as the grinding process progresses in the latter half) (see Figure 5).

[0099] In this case, instead of or in addition to setting the nth monitoring time, the nth threshold value is set to be smaller as the moving speed corresponding to each grinding process becomes slower (i.e., as the grinding process progresses in the latter half) (see FIG. 5).

[0100] In the next step S13, the controller 100 resets the elapsed time counted by the timer 102 to zero, and then starts counting the elapsed time, thereby starting the monitoring process.

[0101] In the following step S14, the controller 100 reads the detection signal of the thickness sensor 101. In this way, the controller 100 obtains the amount of reduction in the thickness D of the workpiece W after the start of the n-th grinding process.

[0102] In the next step S15, the controller 100 determines whether the decrease amount acquired in step S14 exceeds the n-th threshold. This determination corresponds to determining whether the first condition is met. If the determination in step S15 is YES (if the first condition is met), the controller 100 advances the control process to step S16.

[0103] On the other hand, if the determination in step S15 is NO (if the first condition is not met), the controller 100 advances the control process to step S21 in Fig. 6B. In this step S21, the controller 100 acquires, based on the count of the timer 102, the elapsed time since the timer 102 started counting.

[0104] In the following step S22, the controller 100 determines whether the elapsed time acquired in step S21 exceeds the n-th monitoring time. If this determination is NO (if the n-th monitoring time has not been exceeded), the controller 100 returns the control process to step S14 in Fig. 6A. The controller 100 loops the processes in Fig. 6A and 6B until the determination in step S15 or step S22 is YES.

[0105] On the other hand, if the determination in step S22 is YES, in step S23, the controller 100 determines that "there is an abnormality in the rotation of the workpiece W," that is, "the workpiece W is in an unrotated state."

[0106] After that, in the following step S24, the controller 100 notifies the user of the abnormality via the notification unit 104. Furthermore, in the following step S25, the controller 100 causes the pair of grinding wheels 3 to retreat (move away from the workpiece W) via the grinding wheel driving mechanism 4, thereby suspending the grinding of the workpiece W. In this case, the controller 100 ends each of the processes illustrated in FIGS. 6A to 6C.

[0107] Returning to the determination in step S15, if the determination is YES (if the first condition is met), the controller 100 advances the control process to step S16 in FIG. 6A.

[0108] In step S16, the controller 100 determines that "there is no abnormality in the rotation of the workpiece W," that is, that "the workpiece W is not in a non-rotating state." In this case, in the following step S17, the controller 100 continues the rotation of the pair of grinding wheels 3 via the grinding wheel driving mechanism 4, thereby continuing grinding of the workpiece W by the n-th grinding process.

[0109] Next, in step S31 of FIG. 6C following step S17, the controller 100 determines whether the grinding process currently being carried out is a second-type process.

[0110] If the determination in step S31 is YES (if the grinding process is a second-class process), the controller 100 advances the control process in the order of step S32 and step S33. In the former step S32, the controller 100 separates the thickness sensor 101 from the workpiece W.

[0111] In this way, in the second type process, the controller 100 separates the thickness sensor 101 from the workpiece W as soon as the determination in step S15 becomes YES (as soon as the first condition is met).

[0112] On the other hand, if the determination in step S31 is NO (if the grinding process is a first-class process), the controller 100 skips step S32 and advances the control process to step S33. In this case, the thickness sensor 101 maintains contact with the workpiece W. The controller 100 executes sizing processing based on the detection signal of the thickness sensor 101.

[0113] In this way, in the first type process, the controller 100 continues the sizing process using the thickness sensor 101 even after the first condition is met.

[0114] In the following step S33, the controller 100 determines whether or not grinding of the workpiece W by the pair of grinding wheels 3 (specifically, the n-th grinding process) is completed. If this determination is NO, the controller 100 returns the control process to step S33. On the other hand, as soon as the determination in step S33 becomes YES, the controller 100 ends each of the processing steps exemplified in FIGS. 6A to 6C for the n-th grinding process.

[0115] Thereafter, if n=N has not been reached (for example, if the grinding process has not progressed to spark-out), the controller 100 starts the (n+1)th grinding process and starts each of the processing steps exemplified in Figures 6A to 6C for that grinding process. On the other hand, if n=N has been reached (for example, if the grinding process has progressed to spark-out), the controller 100 completes grinding of the workpiece W.

[0116] 11 is a diagram for explaining the determination of the monitoring process. The horizontal axis of Fig. 11 represents the elapsed time from the start of the n-th grinding process, and the vertical axis of the same figure represents the thickness D of the workpiece W.

[0117] If the workpiece W is rotating normally during grinding by the pair of grinding wheels 3, it is considered that the detection value of the thickness sensor 101 gradually decreases (i.e., the amount of decrease in thickness D gradually increases) (see the upper part of FIG. 11). On the other hand, if the workpiece W is not rotating, it is considered that the detection value of the thickness sensor 101 does not decrease more than normal (see the lower part of FIG. 11).

[0118] For example, consider a case where the workpiece W was rotating normally at the start of the nth grinding process, but the rotation of the workpiece W stopped at some point. In this case, as shown in the lower part of Figure 11, until the rotation of the workpiece W stopped, the thickness D decreased at the same rate as in the normal case, as shown in the upper part of the same figure. However, after the time T2 when the rotation of the workpiece W stopped, the thickness D of the workpiece W remained constant.

[0119] In addition, if the rotation of the workpiece W is stopped at the start of the nth grinding process, the thickness D of the workpiece W will remain constant without changing from the start of the process. Also, if the rotation and stopping of the workpiece W are repeated alternately, the thickness D of the workpiece W will repeatedly decrease and remain constant.

[0120] Therefore, according to the embodiment, as illustrated in steps S14 to S15 of Fig. 6A, the controller 100 monitors the amount of decrease in thickness D of the workpiece W based on the detection value of the thickness sensor 101. Furthermore, as illustrated in steps S22 to S23 of Fig. 6B, the controller 100 determines that the workpiece W is in an unrotated state when the amount of decrease does not exceed a predetermined threshold value (n-th threshold value) within a monitoring time (n-th monitoring time).

[0121] 6B, as soon as it is determined that the workpiece W is not rotating, the controller 100 suspends grinding by the pair of grinding wheels 3. This makes it possible to prevent damage to the grinding wheels 3, the workpiece W, and ultimately the entire double disc surface grinding apparatus 1.

[0122] For example, as shown in the upper part of Fig. 11, it is assumed that the decrease in thickness D reaches the n-th threshold value at timing T1 before the elapsed time reaches the n-th monitoring time. In this case, the controller 100 determines that the workpiece W is rotating normally.

[0123] On the other hand, as shown in the lower part of Fig. 11, even at timing T3 when the elapsed time reaches the nth monitoring time, the decrease in thickness D still does not reach the nth threshold value. In this case, the controller 100 determines that the workpiece W is in an unrotated state.

[0124] Furthermore, the monitoring process according to the embodiment can be realized using the conventional thickness sensor 101 for measuring dimensions, without the need to install new sensors. A user of the double disc surface grinding machine 1 can realize the monitoring process by simply devising an appropriate process for the controller 100, without the need to install any new devices.

[0125] Therefore, according to the above embodiment, it is possible to appropriately determine whether the workpiece W of the double-head surface grinding device 1 is in a non-rotating state while achieving space saving for the entire double-head surface grinding device 1, reducing the introduction cost, and reducing the effort required for introduction.

[0126] 5 and 7, the controller 100 executes a monitoring process for each grinding process. This makes it possible to identify the grinding process in which the workpiece W falls into a non-rotating state. Based on the identification results, the user can improve the configuration related to the double disc surface grinding machine 1 and each grinding process performed by the machine 1.

[0127] 6A, the controller 100 restarts counting the elapsed time for each grinding process, thereby enabling the monitoring process to be separated for each grinding process, further improving the ease of use of the monitoring process.

[0128] Furthermore, the slower the cutting speed (=the moving speed) at which the pair of grinding wheels 3 cut into the workpiece W, the more gradually the amount of reduction in the thickness D of the workpiece W increases. Therefore, as shown in Fig. 5, by setting the monitoring time longer in accordance with the gradual increase in the amount of reduction in the thickness D, it is possible to set the monitoring time appropriate for each grinding process. This makes it possible to more accurately determine whether the workpiece W is in a non-rotating state.

[0129] 7, it is possible to individually select a grinding process for which monitoring processing is to be performed from among a plurality of grinding processes. This allows for more flexible settings depending on the type of double disc surface grinding machine 1 and workpiece W. This improves the usability of the monitoring system S.

[0130] Furthermore, it is considered that the thickness D of the workpiece W does not substantially change during the spark-out. Therefore, by excluding the spark-out from the targets for executing the monitoring process, unnecessary processing can be omitted.

[0131] 7, the monitoring time and predetermined threshold value can be changed individually for each grinding process. This allows for more flexible settings depending on the type of double disc surface grinding machine 1 and workpiece W. This improves the usability of the monitoring system S.

[0132] Furthermore, there is a concern that the first and second probes 101a and 101b of the contact-type thickness sensor 101 will wear out over a long period of use. When using a monitoring process, the frequency of contact between the thickness sensor 101 and the workpiece W increases, making such wear even more of a concern.

[0133] 6C, in the second type process, as soon as the first condition is met (i.e., as soon as it is determined that the workpiece W is rotating normally), the thickness sensor 101 is moved away from the workpiece W. This reduces the frequency of contact between the thickness sensor 101 and the workpiece W, and ultimately reduces wear on the thickness sensor 101.

[0134] <Second embodiment> In the above embodiment, the rotation mechanism 2 has been exemplified as having a plurality of outer peripheral rollers 21 and a plurality of rotation roller groups 22, but the present disclosure is not limited to such a rotation mechanism 2. As in the second embodiment described below, the rotation mechanism 2 may be configured to statically support the workpiece W.

[0135] Fig. 8 is a perspective view illustrating a double disc surface grinding machine 1001 according to the second embodiment. Fig. 9 is a side view illustrating the double disc surface grinding machine 1001 according to the second embodiment. Fig. 10 is a front view illustrating the double disc surface grinding machine according to the second embodiment.

[0136] The double disc surface grinding machine 1 according to the above embodiment (first embodiment) and the double disc surface grinding machine 1001 according to the second embodiment have substantially the same configurations of the pair of grinding wheels 3, the controller 100, and the thickness sensor 101. Description of these common elements will be omitted. The workpiece W' is also configured in the same way as the workpiece W according to the first embodiment, except for the configuration related to the notch Wn, which will be described later.

[0137] The double disc surface grinding machine 1001 according to the second embodiment differs from the rotation mechanism 2 according to the first embodiment mainly in the configuration of its rotation mechanism 1002. The rotation mechanism 1002 according to the second embodiment has a ring-shaped carrier 51, a plurality of support rollers 52, and a workpiece drive mechanism 23 similar to that of the first embodiment.

[0138] The workpiece W' is fitted into the inner periphery of the carrier 51. The workpiece W' is fitted into the inner periphery of the carrier 51 and is supported by the carrier 51. As in the above embodiment, the carrier 51 is connected to the workpiece driving mechanism 23 that rotates the carrier 51 around the first central axis O1. The controller 100 rotates the carrier 51 via the workpiece driving mechanism 23.

[0139] Specifically, a notch Wn recessed radially inward is formed on the outer periphery of the workpiece W'. Meanwhile, a protrusion (notch trigger) protruding radially inward is provided on the inner periphery of the carrier 51. By engaging this notch trigger with the notch Wn, the carrier 51 and the workpiece W' rotate integrally.

[0140] The multiple support rollers 52 contact the outer peripheral surface of the carrier 51 to radially support the carrier 51 and the workpiece W'. Specifically, the multiple (four in the illustrated example) support rollers 52 are arranged at different angular positions along the circumferential direction of the workpiece W'.

[0141] The plurality of support rollers 52 come into contact with the outer circumferential surface of the carrier 51 at different angular positions from one another. This contact allows the plurality of support rollers 52 to restrict displacement of the workpiece W' in the radial direction.

[0142] Each support roller 52 rotates around a central axis extending parallel to the first central axis O1. Each support roller 52 also functions as a driven roller that rotates in response to the rotation of the workpiece W'.

[0143] The workpiece holding portion of the carrier 51 is thinner than the finished thickness of the workpiece W' (the target thickness of the workpiece W' when finish grinding is completed).

[0144] Furthermore, both the front and back surfaces of the workpiece W' are supported by a holding mechanism (not shown). This holding mechanism is equipped with a pair of pads that face both surfaces of the workpiece W'. A plurality of discharge ports are opened on the end surface (facing surface) of each pad that faces the workpiece W'. Each discharge port is configured to discharge a fluid (water). Both surfaces of the workpiece W' are supported in a non-contact manner by the pressure of the fluid discharged from each pad.

[0145] In this way, the workpiece W' according to the second embodiment is supported in the radial direction by the carrier 51 and the plurality of support rollers 52, while being statically supported in the axial direction by the fluid. The workpiece W' rotates integrally with the carrier 51.

[0146] In the second embodiment, the notch trigger of the carrier 51 may break off, or the notch Wn of the workpiece W' may come off the notch trigger, resulting in the workpiece W' not rotating.

[0147] Therefore, the double disc surface grinding machine 1 according to the second embodiment, like the first embodiment, is equipped with the monitoring system S illustrated in Fig. 4. This monitoring system S can execute the monitoring method illustrated in Figs. 6A to 6B, etc., and can detect that the workpiece W' is in a non-rotating state, like the first embodiment.

[0148] <Other embodiments> In the above embodiment, the double-disc surface grinding apparatus 1 configured as a horizontal double-disc surface grinding machine is disclosed, but the present disclosure is not limited to such a configuration. The present disclosure can be applied to various double-disc surface grinding apparatuses, such as a vertical surface grinding machine.

[0149] In addition, in the above embodiment, a thin circular semiconductor wafer (silicon wafer) is exemplified as the workpiece W, but the present disclosure is not limited to such a configuration. The workpiece W may be a thin plate made of metal, resin, or the like. In addition, it is not essential that the workpiece W be a thin plate.

[0150] Furthermore, it is not essential that the workpiece W be circular. The workpiece W may have a rectangular shape or a doughnut shape. For example, when applied to a rectangular workpiece W, the opening formed on the inner periphery of the carrier 51 according to the second embodiment may be rectangular in shape depending on the shape of the workpiece W.

[0151] Furthermore, although the above embodiment discloses a contact-type thickness sensor 101, the present disclosure is not limited to such a configuration. The thickness sensor 101 may be any sensor capable of measuring during grinding with the pair of grinding wheels 3, and may also be a non-contact dimension measuring device. The non-contact dimension measuring device may be, for example, a dimension measuring device using a laser. [Explanation of symbols]

[0152] 1 Double-head surface grinding machine 2 Rotation mechanism 21 Multiple outer peripheral rollers 22 Multiple rotating rollers 22a First rotating roller 22b Second rotating roller 23 Work drive mechanism 3 Pair of whetstones 31 First grindstone 32 No. 2 Whetstone 4 Grinding wheel drive mechanism 100 Controllers 101 Thickness sensor (first sensor) 101a First probe 101b Second probe 102 Timer 103 Reception D Work thickness S Surveillance System double work Wn notch 1001 Double-head surface grinding machine 1002 Rotation mechanism 51 Career 52 Multiple support rollers

Claims

1. A monitoring system for a double disc surface grinding machine including a rotation mechanism that operates to support and rotate a workpiece, and a pair of grinding wheels that are arranged to sandwich the workpiece supported by the rotation mechanism and are driven to grind both surfaces of the workpiece, a first sensor disposed to face at least one of the surfaces and configured to detect a thickness between the surfaces of the workpiece during grinding by the pair of grinding wheels; a controller that controls the pair of grinding wheels based on a detection signal from the first sensor, When the amount of reduction in thickness exceeds a predetermined threshold, a first condition is satisfied. The controller a first process for determining whether the first condition is met during operation of the pair of grindstones; a second process of determining that the workpiece is in a non-rotating state and suspending grinding by the pair of grinding wheels when the first condition is not satisfied until the elapsed time from when the determination of the first condition started exceeds a predetermined monitoring time; Perform monitoring operations including A monitoring system for a double disc surface grinding machine.

2. 2. The monitoring system for a double disc surface grinding machine according to claim 1, the controller controls the moving speed of the pair of grinding wheels relative to the workpiece via the pair of grinding wheels so that a plurality of grinding processes, each of which is different for each grinding process, are executed one by one in sequence; The controller is configured to be able to individually execute the monitoring process for each grinding process that constitutes the plurality of grinding processes. A monitoring system for a double disc surface grinding machine.

3. 3. The monitoring system for a double disc surface grinding machine according to claim 2, When the plurality of grinding processes are switched from one grinding process to another grinding process, the controller resets the elapsed time to zero and then starts the monitoring process. A monitoring system for a double disc surface grinding machine.

4. 4. The monitoring system for a double disc surface grinding machine according to claim 3, The monitoring time in the monitoring process is set to be longer as the moving speed corresponding to each grinding process becomes slower. A monitoring system for a double disc surface grinding machine.

5. 3. The monitoring system for a double disc surface grinding machine according to claim 2, a reception unit connected to the controller and configured to receive an operation input from a user; the plurality of grinding processes includes a spark out in which the travel speed is set to zero; the controller is configured to individually switch whether or not to execute the monitoring process for each of the grinding processes excluding the spark-out process based on the operation input; The spark out is excluded from the execution of the monitoring process. A monitoring system for a double disc surface grinding machine.

6. 6. The monitoring system for a double disc surface grinding machine according to claim 5, The controller changes the monitoring time and the predetermined threshold value individually for each of the grinding processes excluding the spark-out process based on the operation input. A monitoring system for a double disc surface grinding machine.

7. 3. The monitoring system for a double disc surface grinding machine according to claim 2, the first sensor is a contact-type thickness sensor that detects the thickness by coming into contact with the workpiece being ground by the pair of grinding wheels, the controller executes a sizing process to determine whether the thickness is within a predetermined range based on the detection signal of the first sensor; the plurality of grinding processes include one or more first type processes that involve the sizing treatment, and one or more second type processes that are performed prior to the first type processes and do not involve the sizing treatment; The controller In the first process, the sizing process is continued even after the first condition is met, During the second process, the first sensor is moved away from the workpiece as soon as the first condition is met. A monitoring system for a double disc surface grinding machine.

8. A monitoring method for a double disc surface grinding machine including a rotation mechanism that operates to support and rotate a workpiece, and a pair of grinding wheels that are arranged to sandwich the workpiece supported by the rotation mechanism and rotate to grind both surfaces of the workpiece, comprising: a first sensor disposed to face at least one of the surfaces and configured to detect a thickness between the surfaces of the workpiece during grinding by the pair of grinding wheels; a controller that controls the pair of grinding wheels based on a detection signal from the first sensor; When the amount of reduction in thickness exceeds a predetermined threshold, a first condition is satisfied. The controller: a first process for determining whether the first condition is met during operation of the pair of grindstones; a second process of determining that the workpiece is in a non-rotating state and suspending grinding by the pair of grinding wheels when the first condition is not satisfied until the elapsed time from when the determination of the first condition started exceeds a predetermined monitoring time; Perform monitoring operations including A method for monitoring a double disc surface grinding machine.

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