Suction holding monitoring method and processing apparatus

Abstract

To detect a minute leakage on a holding surface when performing processing by suction-holding a workpiece on the holding surface of a chuck table.SOLUTION: A suction holding monitoring method executes: a placement step of placing a workpiece (W) on a holding surface (421) of a chuck table (14); a suction holding recognition step of making the holding surface communicate with a suction source (45), recognizing that the holding surface suction-holds the workpiece when a value of a pressure gauge (47) exceeds a preset threshold (S) in the negative pressure direction, and recognizing that the holding surface does not suction-hold the workpiece when the value of the pressure gauge does not exceed the threshold in the negative pressure direction; and a suction holding monitoring step of recognizing that a leakage has occurred on the holding surface when the value of the pressure gauge after recognizing that the holding surface suction-holds the workpiece in the suction holding recognition step varies more greatly than a preset monitoring width (Pa) and recognizing that the leakage has not occurred on the holding surface when the value does not vary more greatly than the monitoring width.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a suction holding monitoring method for monitoring the suction holding of a workpiece by a chuck table, and a processing apparatus for processing a workpiece held on the chuck table.

Background Art

[0002] A grinding apparatus for grinding a plate-shaped workpiece with a grinding wheel performs processing in a state where a suction force is applied to a holding surface of a chuck table that holds the workpiece, and the workpiece is suction-held on the holding surface of the chuck table.

[0003] When a workpiece having a modified layer formed inside by laser processing is placed on the holding surface of the chuck table, the upper surface becomes concave and the lower surface becomes convex, and the outer peripheral portion of the workpiece is in a state of warping upward. When suction-holding a workpiece having an element that warps the outer peripheral portion on the holding surface, water is supplied between the holding surface and the workpiece to form a water seal on the outer periphery of the workpiece, and the workpiece is suction-held on the holding surface so that the outer peripheral portion of the workpiece does not float (for example, Patent Document 1).

[0004] In addition, the holding surface of the chuck table of the grinding apparatus has a gentle conical shape (circular in plan view), and a square (rectangular) workpiece may be held on such a holding surface and the workpiece may be ground (for example, Patent Documents 2 and 3).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] When a workpiece with a tendency to warp is rectangular, the corners of the workpiece, which are held by suction on the chuck table, tend to lift up due to reasons such as the water seal running out, causing a slight leak (leakage of suction force) on the holding surface. As a result, the corners of the workpiece may flap against the holding surface.

[0007] Furthermore, with rectangular workpieces, the shape of the workpiece and the holding surface do not match due to rotational misalignment between the workpiece and the holding surface, which can lead to minute leaks at the corners of the workpiece.

[0008] If a small leak occurs on the holding surface and grinding begins with the corners of the workpiece lifted, the grinding wheel will contact the corners of the workpiece first. This can lead to uneven grinding between the corners and other parts of the workpiece, or even damage to the corners.

[0009] Furthermore, even in processing equipment other than grinding machines, when processing is performed by holding the workpiece by suction on the holding surface of the chuck table, it is necessary that the workpiece is securely held by suction. Therefore, the same problem exists in all processing equipment that holds workpieces by suction on the holding surface of the chuck table.

[0010] The present invention has been made in view of the above, and aims to provide a suction holding monitoring method and a processing apparatus that can detect minute leaks on the holding surface when a workpiece is held by suction on the holding surface of a chuck table and processed. [Means for solving the problem]

[0011] One aspect of the present invention involves connecting the holding surface of a chuck table and a suction source via a communication passage, and the holding surface is controlled by the value of a pressure gauge placed in the communication passage. squareA suction holding monitoring method for monitoring whether a workpiece is being held by suction, comprising: a placement step of placing a workpiece on the holding surface; a suction holding recognition step of connecting the holding surface and a suction source, and recognizing that the holding surface is holding the workpiece by suction if the value of the pressure gauge exceeds a preset threshold in the negative pressure direction, and recognizing that the holding surface is not holding the workpiece by suction if the value of the pressure gauge does not exceed the threshold in the negative pressure direction; and in the suction holding recognition step, A water seal forming step involves supplying water to the holding surface, which is in communication with the suction source, and to the workpiece placed on the holding surface, to form a water seal, and after the water seal is formed, The system comprises a suction holding monitoring step in which, after the holding surface recognizes that it has suction-held the workpiece, if the value of the pressure gauge fluctuates by a preset monitoring range, it is recognized that a leak has occurred in the holding surface, and if the value does not fluctuate by a preset monitoring range, it is recognized that no leak has occurred in the holding surface.

[0012] Applicable In the suction retention monitoring process, After the water seal is formed, The chuck table may be rotated around the center of the holding surface as an axis, thereby applying centrifugal force to the water.

[0013] The monitoring range can be defined as the range between the moving average value of the pressure gauge within a predetermined time range and a value that is further away from the moving average value in the positive pressure direction.

[0014] One aspect of the present invention is a processing apparatus capable of the above-described suction holding and monitoring method, wherein the holding surface square The apparatus comprises a chuck table for holding a workpiece, a processing unit for processing the workpiece held on the holding surface, a communication passage connecting the holding surface and a suction source, a pressure gauge disposed in the communication passage for measuring the pressure within the passage, a suction holding determination unit that determines the holding surface has suction-held the workpiece if the value of the pressure gauge exceeds a preset threshold in the negative pressure direction, a leak determination unit that determines no leak has occurred on the holding surface if the value of the pressure gauge does not exceed a preset monitoring width, and determines a leak has occurred on the holding surface if the value of the pressure gauge exceeds a preset monitoring width, and a control unit that stops the apparatus if the leak determination unit determines a leak has occurred on the holding surface. One configuration includes a water seal nozzle that supplies water to the corners of a workpiece placed on the holding surface, which is in communication with the suction source, thereby forming a water seal. [Effects of the Invention]

[0015] According to the suction holding monitoring method and the processing apparatus of the present invention, it is possible to detect a minute leak on the holding surface of the chuck table and prevent breakage of the workpiece and failure of processing due to performing processing in an incomplete holding state.

Brief Description of the Drawings

[0016] [Figure 1] It is a perspective view of a grinding apparatus. [Figure 2] It is a cross-sectional view showing a part of the grinding apparatus. [Figure 3] It is a graph for explaining the suction holding recognition process. [Figure 4] It is a graph for explaining the suction holding monitoring process. [Figure 5] It is a graph for explaining the suction holding monitoring process.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the suction holding monitoring method and the processing apparatus according to the present embodiment will be described with reference to the accompanying drawings. FIG. 1 shows a grinding apparatus 1 which is an example of a processing apparatus to which the present invention is applied, and FIG. 2 shows a part of the grinding apparatus 1. FIGS. 3 to 5 are graphs for explaining the suction holding monitoring method performed by the grinding apparatus 1.

[0018] The grinding apparatus 1 performs grinding on a workpiece W which is a work piece. The workpiece W has a plurality of silicon chips arranged on a PCB (Printed Circuit Board) substrate and is molded with resin so as to seal the silicon chips, and has a rectangular (square) plate shape. In the grinding apparatus 1, the surface of the workpiece W on the side opposite to the side where the silicon chips are arranged is ground. In the following description, the surface to be ground in the grinding apparatus 1 is defined as the upper surface Wa of the workpiece W, and the surface on the opposite side is defined as the lower surface Wb. [[ID=​The grinding device 1 is configured to perform a series of operations on the workpiece W, consisting of loading, grinding, cleaning, and unloading, all fully automatically. The workpiece W is loaded into the grinding device 1 while contained in a cassette C. The workpiece W loaded into the grinding device 1 has a concave top surface Wa and its corners (four corners) are curved upwards (see Figure 2).

[0020] In the grinding device 1, the X-axis, Y-axis, and Z-axis directions are perpendicular to each other. The X-axis and Y-axis directions are approximately horizontal, while the Z-axis direction is vertical. Of the two arrows indicating the X-axis direction, the +X side is forward and the -X side is backward. Of the two arrows indicating the Y-axis direction, the +Y side is left and the -Y side is right. Of the two arrows indicating the Z-axis direction, the +Z side is upward and the -Z side is downward.

[0021] Two cassettes C, capable of accommodating multiple workpieces W, are mounted on the front of the base 10 of the grinding device 1. One cassette C contains workpieces W before grinding, and the other cassette C contains workpieces W after grinding. Behind the cassettes C, a robot hand 11 is provided for loading and unloading workpieces W into and out of the cassettes C. To the left and right and diagonally behind the robot hand 11, there is a temporary storage table 12 for placing workpieces W before grinding and a spin cleaning mechanism 13 for cleaning the ground workpieces W. The robot hand 11 transports workpieces W before grinding from the cassettes C to the temporary storage table 12 and transports ground workpieces W from the spin cleaning mechanism 13 to the cassettes C.

[0022] The workpiece W, transported to the temporary placement table 12 by the robot hand 11, is positioned so that it is in a predetermined position relative to the temporary placement table 12.

[0023] The spin cleaning mechanism 13 is equipped with a nozzle 132 that sprays cleaning water and drying air toward the spinner table 131. In the spin cleaning mechanism 13, cleaning water is sprayed from the nozzle 132 toward the workpiece W held on the spinner table 131 to clean the workpiece W, and after cleaning, drying air is blown from the nozzle 132 to dry the workpiece W.

[0024] Between the temporary storage table 12 and the spin cleaning mechanism 13 in the Y-axis direction, there is a first transport mechanism 15 that transports the workpiece W before grinding from the temporary storage table 12 to the chuck table 14, and a second transport mechanism 16 that transports the ground workpiece W from the chuck table 14 to the spin cleaning mechanism 13. The first transport mechanism 15 and the second transport mechanism 16 each use a transport pad to suck and hold the workpiece W from above, and transport the workpiece W by causing a support arm that supports the transport pad to rotate around an axis in the Z-axis direction and to move up and down in the Z-axis direction.

[0025] A rectangular opening extending in the X-axis direction is formed on the upper surface of the base 10 at the rear of the grinding device 1. This opening is covered by a movable plate 17 that can move in the X-axis direction together with the chuck table 14 and a bellows-shaped waterproof cover 18.

[0026] Below the waterproof cover 18, a table movement mechanism 20 is provided for moving the chuck table 14 in the X-axis direction. The table movement mechanism 20 comprises a pair of guide rails 21 extending in the X-axis direction and a ball screw 22, and the mobile table 23 is supported so as to be movable along the guide rails 21. The ball screw 22 is screwed into a threaded portion (not shown) of the mobile table 23, and when the motor 24 operates and the ball screw 22 is rotated, the mobile table 23 moves in the X-axis direction.

[0027] Furthermore, a table rotation mechanism 30 for rotating the chuck table 14 is provided below the waterproof cover 18. As shown in Figure 2, the table rotation mechanism 30 has a table rotation shaft 32 rotatably supported via a bearing 38 inside a support frame 31 supported on the movable table 23. An endless belt 36 is wrapped around a driven pulley 33 provided on the outer surface of the table rotation shaft 32 and a drive pulley 35 rotated by a motor 34. When the drive pulley 35 is rotated by the operation of the motor 34, the rotation is transmitted to the driven pulley 33 via the endless belt 36, and the table rotation shaft 32 is rotated. The chuck table 14 is detachable from a table base 37 provided on the upper part of the table rotation shaft 32, and when the chuck table 14 is attached to the table base 37, the chuck table 14 rotates together with the table rotation shaft 32.

[0028] The chuck table 14 comprises a frame 40 and a disc-shaped porous plate 42 mounted in a recess 41 on the upper side of the frame 40. The porous plate 42 is made of a porous material such as ceramics, and fine pores are formed throughout its entire surface. With the porous plate 42 mounted in the recess 41 of the frame 40, the upper surface of the frame 40 and the upper surface of the porous plate 42 are flush. The upper surface of the porous plate 42 constitutes a holding surface 421 that holds the workpiece W by suction.

[0029] The suction structure in the chuck table 14 will be explained primarily with reference to Figure 2. A communication passage 44 is formed inside the chuck table 14 and inside the table rotation shaft 32. The communication passage 44 communicates with the bottom of the recess 41 of the frame 40 and extends downward from the recess 41. A suction pipe 39 is connected to a rotary joint 321 provided at the lower end of the table rotation shaft 32, and the communication passage 44 is connected to the suction pipe 39. In other words, the suction pipe 39 constitutes part of the communication passage 44. The suction pipe 39 is connected to a suction source 45 via an on / off valve 46.

[0030] When the on / off valve 46 is opened and the suction source 45 is activated, air is drawn in from the recess 41 through the communication passage 44, and a suction force acts on the holding surface 421 of the porous plate 42 held in the recess 41. In other words, the communication passage 44 connects the holding surface 421 and the suction source 45. A pressure gauge 47 for measuring the pressure inside the communication passage 44 is provided in the middle of the suction pipe 39.

[0031] Furthermore, the communication passage 44 is connected to an air supply source 80 via an on / off valve 82 and to a water supply source 81 via an on / off valve 83. When the on / off valve 82 is opened and the air supply source 80 is activated, air supplied via the communication passage 44 is ejected from the holding surface 421. When the on / off valve 83 is opened and the water supply source 81 is activated, water supplied via the communication passage 44 is ejected from the holding surface 421. It is also possible to activate the air supply source 80 and the water supply source 81 simultaneously to eject a mixed fluid of air and water from the holding surface 421.

[0032] Returning to Figure 1, the grinding mechanism 50 and the lifting mechanism 60 will be explained. A lifting mechanism 60 is provided on a column 19 erected at the rear of the base 10 to move the grinding mechanism 50 up and down in the Z-axis direction.

[0033] The lifting mechanism 60 includes a pair of guide rails 61 positioned on the front side of the column 19 and extending in the Z-axis direction, a lifting table 62 installed to be movable in the Z-axis direction relative to the pair of guide rails 61, and a ball screw 63 extending in the Z-axis direction and screwed into a threaded portion (not shown) of the lifting table 62. The ball screw 63 is rotated by the driving force of a motor 64 connected to one end of the ball screw 63, causing the lifting table 62 to move in the Z-axis direction.

[0034] The grinding mechanism 50 is mounted on the front of the lifting table 62 via a holder 51, and rotatably supports the spindle 53 with respect to the spindle housing 52 supported by the holder 51. The spindle 53 rotates about its axis in the Z-axis direction by the driving force of the spindle motor 54.

[0035] A mount 55 is connected to the lower end of the spindle 53, and a grinding wheel 56 is mounted on the mount 55. Multiple grinding wheels 57 are arranged in an annular pattern on the lower surface of the grinding wheel 56. The grinding mechanism 50 grinds the upper surface Wa of the workpiece W, which is held by suction to the holding surface 421 of the chuck table 14, using the grinding wheels 57.

[0036] As shown in Figure 2, the grinding mechanism 50 is provided with a grinding water channel 58 that supplies grinding water to an opening on the lower side of the grinding wheel 56. The grinding water channel 58 is connected to a grinding water source 59, and the grinding water sent from the grinding water source 59 passes through the grinding water channel 58 and is discharged from the opening on the lower side of the grinding wheel 56.

[0037] A thickness measuring device 43 is mounted on the base 10. The thickness measuring device 43 includes a first height gauge that measures the height position of the upper surface Wa of the workpiece W held on the holding surface 421 of the chuck table 14, and a second height gauge that measures the height position of the upper surface of the frame 40 of the chuck table 14. The thickness of the workpiece W is measured based on the difference between the measurement value of the first height gauge and the measurement value of the second height gauge.

[0038] A water seal nozzle 48 is supported on the support frame 31, which supplies water M to the holding surface 421 and the workpiece W. The water seal nozzle 48 sprays water M supplied from the water supply source 49 onto the holding surface 421 and the workpiece W from the side.

[0039] Each part of the grinding machine 1 is controlled by the control unit 70 (Figure 2). The control unit 70 consists of a processor that performs various processes and a memory that records programs and temporary data. Figure 2 shows only the connection relationship between the control unit 70 and the pressure gauge 47, but the control unit 70 is also connected to send and receive signals to other parts of the device besides the pressure gauge 47.

[0040] The control unit 70 controls the grinding feed amount, grinding feed speed, and rotational speed of the grinding wheel 56 of the grinding mechanism 50 in the Z-axis direction according to a control program stored in memory, and performs grinding until the thickness of the workpiece W, as measured by the thickness measuring instrument 43, reaches the finish thickness. The control unit 70 also controls the transport operation of the workpiece W by the robot hand 11, the first transport mechanism 15, and the second transport mechanism 16, as well as the cleaning operation of the workpiece W by the spin cleaning mechanism 13. In the operation of each part of the grinding apparatus 1 described below, unless the main control entity is specified, it is assumed that the operation is controlled by control signals sent from the control unit 70.

[0041] In the grinding apparatus 1, the robot hand 11 removes the ungrinded workpiece W from the cassette C and transports it to the temporary storage table 12. Subsequently, the transport pad of the first transport mechanism 15 sucks and holds the upper surface Wa of the workpiece W, and the first transport mechanism 15 loads the workpiece W from the temporary storage table 12 onto the chuck table 14. When the workpiece W is transferred from the transport pad of the first transport mechanism 15, the chuck table 14 is positioned near the first transport mechanism 15 (towards the front in the X-axis direction) by the drive of the table movement mechanism 20.

[0042] As shown in Figure 2, the workpiece W conveyed by the first conveying mechanism 15 is placed on the holding surface 421 of the chuck table 14. When the on / off valve 46 is opened, the suction source 45 communicates with the communication passage 44, and by operating the suction source 45, a suction force acts on the holding surface 421 of the chuck table 14. This suction force causes the workpiece W to be held in place by suction on the holding surface 421. When the suction force is applied appropriately to the workpiece W, the entire workpiece W conforms to the shape of the holding surface 421, and the warping is eliminated.

[0043] When the holding surface 421 suction-holds the workpiece W, water M is supplied from the water seal nozzle 48 to form a water seal between the holding surface 421 and the workpiece W. Due to the effect of the water seal, the outer periphery (four corners) of the workpiece W is more easily attracted to the holding surface 421.

[0044] The chuck table 14, which holds the workpiece W by suction, is moved to the rearward side in the X-axis direction by the table moving mechanism 20, and positioned at the machining position below the grinding mechanism 50.

[0045] Next, the lifting mechanism 60 lowers the grinding mechanism 50 to bring the grinding wheel 57 into contact with the upper surface Wa of the workpiece W. The spindle 53 rotates the grinding wheel 56, and the table rotation mechanism 30 rotates the chuck table 14 around the center of the holding surface 421, grinding the upper surface Wa of the workpiece W while pressing it with the grinding wheel 57. During grinding, grinding water is supplied from the grinding water source 59 via the grinding water channel 58 to wash away grinding debris. The grinding water is also used to cool the area around the grinding site. Additionally, water M may be supplied from the water seal nozzle 48 during grinding.

[0046] When the thickness of the workpiece W, as measured by the thickness measuring instrument 43, reaches a preset finish thickness, the rotation of the grinding wheel 56 in the grinding mechanism 50, the rotation of the chuck table 14 by the table rotation mechanism 30, and the grinding feed of the grinding mechanism 50 by the lifting mechanism 60 are stopped. Then, the grinding mechanism 50 is raised by the lifting mechanism 60 to separate the grinding wheel 57 from the workpiece W on the chuck table 14, and the grinding process is completed.

[0047] After grinding, the chuck table 14 is moved forward in the X-axis direction by the table moving mechanism 20, positioning it at a transfer position near the second conveying mechanism 16. The on / off valve 46 is closed, disconnecting the holding surface 421 from the suction source 45. Since the suction force from the holding surface 421 to the workpiece W is no longer applied, the workpiece W can be transferred from the chuck table 14 to the second conveying mechanism 16. When transferring the workpiece W from the chuck table 14 to the second conveying mechanism 16, the air supply source 80 may be activated to open the on / off valve 82, and the water supply source 81 may be activated to open the on / off valve 83, causing a mixed fluid of air and water to be ejected from the holding surface 421 to push up the workpiece W.

[0048] The second transport mechanism 16 removes the workpiece W from the chuck table 14 and transports it to the spin cleaning mechanism 13. The spin cleaning mechanism 13 then cleans the workpiece W. Subsequently, the cleaned workpiece W is removed from the spinner table 131 by the robot hand 11 and placed in the cassette C.

[0049] In the grinding apparatus 1, which performs the series of operations as described above, when grinding the workpiece W with the grinding wheel 57 of the grinding mechanism 50, the entire lower surface Wb of the workpiece W needs to be held by suction on the holding surface 421 of the chuck table 14. In particular, in the case of the workpiece W of this embodiment, which has elements that curl up at the outer circumference (four corners), the outer circumference of the workpiece W may not be able to be securely held in contact with the holding surface 421 by suction force alone. Therefore, water M is supplied from the water seal nozzle 48 to the holding surface 421 and the workpiece W, and the outer circumference of the workpiece W is held by suction on the holding surface 421 by the effect of the water seal.

[0050] However, if the workpiece W, which has elements that can bend upwards, is rectangular, when it is moved to the rearward side in the X-axis direction by the table moving mechanism 20 and positioned at the machining position below the grinding mechanism 50, or when the chuck table 14 is rotated when grinding is started, the corners of the workpiece W, which is being held by suction, tend to lift up due to reasons such as the water in the water seal running out, and a small leak may occur in the area of ​​the holding surface 421 corresponding to the corners of the workpiece W. In addition, because the shapes of the rectangular workpiece W and the circular holding surface 421 in plan view do not match, the suction force does not act uniformly on the workpiece W, and a small leak may occur in the holding surface 421 near the corners of the workpiece W. At this time, although a small leak is occurring in the corners, the suction force of the holding surface 421 exceeds a preset threshold, so the grinding device 1 determines that the holding surface 421 is holding the workpiece W by suction and starts grinding.

[0051] If a slight leak occurs in the suction force of the holding surface 241 and grinding is started with the corners of the workpiece W lifted up, the grinding wheel 57 may come into contact with the corners of the workpiece W first, potentially resulting in uneven grinding between the corners and other parts, or even damage to the corners.

[0052] To resolve these issues, the grinding apparatus 1 of this embodiment monitors the suction holding state of the workpiece W by the chuck table 14 and determines whether or not minute leaks occur on the holding surface 421. The suction holding state of the workpiece W is monitored by the control unit 70 by referring to the measurement results of the pressure gauge 47. The control unit 70 has a suction holding determination unit 71, a leak determination unit 72, and a control unit 73 as functional blocks related to monitoring the suction holding state of the workpiece W.

[0053] Figures 3 to 5 are graphs illustrating the suction holding and monitoring method for workpiece W. The vertical axis of each graph represents the value of the pressure gauge 47, with the upper part representing negative pressure and the lower part representing positive pressure. The horizontal axis of each graph represents the passage of time, with time progressing to the right.

[0054] The suction holding and monitoring method may be performed before grinding the workpiece W by the grinding mechanism 50, or it may be performed during the grinding of the workpiece W. Specifically, the suction holding and monitoring method includes the following steps.

[0055] [Placement Process] In the loading process, the workpiece W is placed on the holding surface 421 of the chuck table 14. If the workpiece W has a concave upper surface Wa, when the lower surface Wb (or the protective member if the lower surface Wb is covered by a protective member) of the workpiece W is placed on the holding surface 421, the outer circumference of the workpiece W will be curved upwards (see Figure 2).

[0056] [Suction holding recognition process] Next, the suction holding recognition process is performed. In the suction holding recognition process, the suction source 45 is activated and the on / off valve 46 is opened to connect the suction source 45 and the holding surface 421 via the communication passage 44, thereby applying a suction force to the holding surface 421. The workpiece W is held in place by the suction force on the holding surface 421.

[0057] The suction holding and recognition process may include a water seal formation process in which water M is supplied to the holding surface 421 and the workpiece W to form a water seal. The water seal formation process is carried out by spraying water M supplied from a water supply source 49 into the gap between the holding surface 421 and the lower surface Wb of the workpiece W from a water seal nozzle 48. This forms a water seal over the entire outer circumference of the workpiece W, thereby enhancing the effect of suction holding of the outer circumference of the workpiece W to the holding surface 421. At least four water seal nozzles 48 are arranged around the chuck table 14, and each water seal nozzle 48 is positioned to spray water onto the corners of the workpiece W (only one water seal nozzle 48 is shown in Figures 1 and 2).

[0058] The water seal nozzle 48 may be formed in a ring shape and may have multiple nozzles for spraying water onto the outer circumference of the workpiece W.

[0059] Alternatively, the on / off valve 83 may be opened to supply water from the water supply source 81 to the holding surface 421, forming a water layer on the holding surface 421. Then, the lower surface Wb of the workpiece W may be brought into contact with the holding surface 421, and with a water seal formed, the holding surface 421 may be connected to the suction source 45, thereby suctioning and holding the workpiece W while suctioning the water on the holding surface 421.

[0060] The suction holding determination unit 71 of the control unit 70 continuously monitors the value of the pressure gauge 47, or at predetermined time intervals. If the value of the pressure gauge 47 exceeds a preset threshold in the negative pressure direction, it recognizes that the holding surface 421 has suction-held the workpiece W. If the value of the pressure gauge 47 does not exceed the threshold in the negative pressure direction, it recognizes that the holding surface 421 is not suction-held the workpiece W.

[0061] Figure 3 is a graph illustrating a specific example of the suction holding determination made by the suction holding determination unit 71. Based on various conditions such as the shape and size of the workpiece W, the shape and size of the holding surface 421, and the performance of the suction source 45, a threshold S indicating a predetermined pressure value in the vertical axis direction is pre-set. The threshold S is stored in the memory of the control unit 70. Note that the threshold S shown in Figure 3 is merely an example, and the threshold will be a different value depending on the differences in the above conditions.

[0062] As a result of performing the suction holding recognition process on separate workpieces W, the measured values ​​Ra and Rb shown in Figure 3 were obtained for the pressure gauge 47. The suction holding determination unit 71 recognizes that the holding surface 421 has suction-held the workpiece W if the measured value Ra exceeds the threshold S in the negative pressure direction. On the other hand, the suction holding determination unit 71 recognizes that the holding surface 421 has not suction-held the workpiece W if the measured value Rb does not exceed the threshold S in the negative pressure direction.

[0063] Furthermore, even if the holding surface 421 is not suction-holding the workpiece W, the value of the pressure gauge 47 may momentarily exceed the threshold S in the negative pressure direction due to some reason such as a temporary blockage of the communication passage 44. To take such cases into consideration, when the suction-holding determination unit 71 recognizes that the holding surface 421 is suction-holding the workpiece W, the condition for the determination may include that the state of exceeding the threshold S continues for a predetermined period of time or longer.

[0064] If the suction holding determination unit 71 determines in the suction holding recognition step that the holding surface 421 is not holding the workpiece W by suction, the control unit 70 may use the notification unit provided by the grinding device 1 to notify that the workpiece W is not being held by suction. Specific examples of notification by the notification unit include display on the operation panel of the grinding device 1, lighting up a lamp on the grinding device 1 (including changes in lighting patterns such as blinking), and sounding an audible signal from the speaker of the grinding device 1.

[0065] [Suction holding monitoring process] In the suction holding recognition process, if the suction holding determination unit 71 determines that the holding surface 421 has held the workpiece W by suction, the suction holding monitoring process is performed. The suction holding monitoring process is carried out by rotating the chuck table 14 around the center of the holding surface 421 and applying centrifugal force to the water M supplied from the water seal nozzle 48. In the suction holding recognition process, the leak determination unit 72 of the control unit 70 determines whether or not there is a leak in the holding surface 421 based on the relationship between the value of the pressure gauge 47 after the holding surface 421 has recognized that it has held the workpiece W by suction, and the pressure value monitoring range described later.

[0066] Alternatively, the suction holding and monitoring process may be performed while the chuck table 14 is rotated and water M is sprayed from the water seal nozzle 48. Or, instead of spraying water M from the water seal nozzle 48, the chuck table 14 may be moved directly below the grinding mechanism 50, and the suction holding and monitoring process may be performed while the chuck table 14 is rotated and grinding water is supplied from the grinding mechanism 50.

[0067] Alternatively, the suction holding and monitoring process may be performed without rotating the chuck table 14.

[0068] When suction force is applied to the holding surface 421, various states occur, such as a state in which air is sucked in, a state in which grinding water remaining on the holding surface 421 is sucked in, or a state in which water M supplied from the water seal nozzle 48 is sucked in. The pressure inside the communication passage 44 and the suction pipe 39 changes depending on whether air (gas) or water (liquid) is sucked in, so the value of the pressure gauge 47 fluctuates. A monitoring range is set to distinguish between the fluctuation of the pressure gauge 47 value caused by such normal suction and the fluctuation of the pressure gauge 47 value caused by an unusual leak, and to isolate and recognize the occurrence of a leak.

[0069] Figure 4 is a graph illustrating a specific example of the first form of suction holding monitoring performed by the leak detection unit 72. Based on various conditions such as the shape and size of the workpiece W, the shape and size of the holding surface 421, and the performance of the suction source 45, the upper and lower limits of the pressure fluctuation monitoring range Pa are pre-set. The monitoring range Pa is stored in the memory of the control unit 70. Note that the monitoring range Pa shown in Figure 4 is merely an example, and the monitoring range will be different depending on the differences in the above conditions.

[0070] In the first form of suction holding monitoring, if the value of the pressure gauge 47 fluctuates by a greater than a preset monitoring range Pa, it is recognized that a leak has occurred on the holding surface 421. If the value does not fluctuate by a greater than the monitoring range Pa, it is recognized that no leak has occurred on the holding surface 421.

[0071] For example, when a suction holding monitoring process was performed on a certain workpiece W, the measured value Rc shown in Figure 4 was obtained for the pressure gauge 47. The measured value Rc includes deviation portions Da, Db, and Dc that exceed the monitoring width Pa in the positive pressure direction. In other words, the measured value Rc is fluctuating more than the monitoring width Pa. Therefore, based on the presence of deviation portions Da, Db, and Dc, the leak determination unit 72 determines that a leak has occurred on the holding surface 421.

[0072] Figure 5 is a graph illustrating a specific example of the second form of suction holding monitoring performed by the leak detection unit 72. In the second form, the monitoring width Pb is set as the width between the moving average value Qa of the pressure gauge 47 within a preset time range T and a value Qb that is away from the moving average value Qa in the positive pressure direction. Since the negative pressure boundary of the monitoring width Pb is the moving average value Qa within the time range T, changing the start point Ta and end point Tb of the time range T along the horizontal axis of the graph will change the position of the monitoring width Pb along the vertical axis of the graph according to the pressure fluctuations within that time range T.

[0073] The size of the monitoring width Pb in the vertical axis direction of the graph in Figure 5 (the difference from the moving average value Qa to the value Qb that is farther away in the positive pressure direction) is set based on various conditions such as the shape and size of the workpiece W, the shape and size of the holding surface 421, and the performance of the suction source 45.

[0074] Then, similar to the first embodiment described above, if the value of the pressure gauge 47 fluctuates by a larger amount than the monitoring range Pb, it is recognized that a leak has occurred in the retaining surface 421, and if it does not fluctuate by a larger amount than the monitoring range Pb, it is recognized that no leak has occurred in the retaining surface 421.

[0075] For example, when a suction holding monitoring process was performed on a certain workpiece W, the measured value Rd shown in Figure 5 was obtained for the pressure gauge 47. In the measured value Rd, at the end point Tb of the time range T, the value of the pressure gauge 47 exceeds the monitoring width Pb in the positive pressure direction and fluctuates more than the monitoring width Pb, so the leak determination unit 72 determines that a leak has occurred on the holding surface 421.

[0076] Even with workpieces W of the same shape and size, differences in the orientation of the workpiece W on the holding surface 421 (rotational displacement) can cause differences in the likelihood of leakage during suction holding. Taking this into consideration, the second form of suction holding monitoring shown in Figure 5 does not use a preset monitoring width (monitoring width Pa in Figure 4), but rather uses a dynamic monitoring width Pb based on a moving average value Qa divided by a time range T to monitor how much the pressure value has changed compared to the most recent state (time range T). This allows for highly accurate detection optimized for the conditions of each individual workpiece W, making it possible to determine the occurrence of leakage more reliably.

[0077] The suction holding monitoring process is performed as described above. If the leak detection unit 72 determines that a leak has occurred on the holding surface 421 during the suction holding monitoring process, the control unit 73 of the control unit 70 stops the grinding device 1 and prevents grinding from being performed on the workpiece W on the holding surface 421 where the leak was detected. If grinding is already in progress, the control unit prevents further grinding.

[0078] The stopping of the grinding device 1 by the control unit 73 means that at least the operations performed when grinding the workpiece W with the grinding wheel 57 are not performed, such as the downward grinding feed of the grinding mechanism 50 by the lifting mechanism 60, the rotation of the grinding wheel 56 in the grinding mechanism 50, and the rotation of the chuck table 14 by the table rotation mechanism 30.

[0079] In other words, if grinding is carried out while a leak occurs in the holding surface 421 and the outer circumference of the workpiece W is lifted away from the holding surface 421, problems such as uneven thickness of the workpiece W or damage to the workpiece W will occur. Therefore, operations that directly lead to such problems are stopped when a leak in the holding surface 421 is detected. On the other hand, operations and controls that do not cause actual harm even if the workpiece W is lifted away from the holding surface 421 may be continued without stopping. For example, operations such as cleaning the workpiece W with the spin cleaning mechanism 13 after proper grinding is completed, or storing the cleaned workpiece W in the cassette C with the robot hand 11, may be continued if it is determined that a leak has occurred in the holding surface 421.

[0080] If the leak detection unit 72 determines that a leak has occurred on the holding surface 421 during the suction holding monitoring process, the control unit 70 may use the notification unit provided by the grinding device 1 to notify the system of the leak.

[0081] If the leak detection unit 72 determines that no leak has occurred on the holding surface 421 during the suction holding monitoring process, grinding is performed on the workpiece W. In this case, since the entire workpiece W, including the four corners, is held by suction without lifting from the holding surface 421, the workpiece W can be properly ground.

[0082] As described above, the suction holding monitoring method and the grinding apparatus capable of this suction holding monitoring method of this embodiment can detect minute leaks on the holding surface 421 of the chuck table 14, enabling highly accurate grinding of the workpiece W. Since the suction holding monitoring method is executed to detect minute leaks on the holding surface 421 before the grinding wheel 57 contacts the workpiece W during grinding, damage to the workpiece W can be prevented. Furthermore, by executing the suction holding monitoring method during grinding, it is possible to prevent damage to the workpiece W caused by continuing grinding in the presence of a leak.

[0083] Furthermore, it is possible to detect minute leaks caused by misalignment of the rectangular workpiece W relative to the holding surface 421 in the rotational direction of the chuck table 14.

[0084] Furthermore, even when holding a circular workpiece instead of a rectangular one, a small leak may occur if the workpiece's position shifts parallel to the holding surface 421. However, the above-described suction holding and monitoring method can detect even such small leaks. In other words, the present invention is useful even when the shape of the workpiece is not rectangular.

[0085] The above embodiment was applied to a grinding apparatus 1 that uses a grinding wheel 57 as the processing unit for processing the workpiece W, but the present invention can also be applied to processing apparatuses other than grinding apparatuses. Various devices such as cutting apparatuses and polishing apparatuses are known as processing apparatuses that hold a workpiece by suction to the holding surface of a chuck table. In these apparatuses as well, processing such as cutting and polishing is performed while the workpiece is held by suction to the holding surface, so the usefulness of the present invention, which can detect minute leaks on the holding surface, is high.

[0086] Furthermore, the embodiments of the present invention are not limited to the embodiments and modifications described above, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Moreover, if the technical idea of ​​the present invention can be realized in a different way by advances in the art or by other derived arts, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention. [Industrial applicability]

[0087] As described above, the suction holding monitoring method and processing apparatus of the present invention can detect minute leaks on the holding surface of the chuck table, thereby preventing damage to the workpiece during processing and preventing processing failures. It is particularly useful when processing workpieces that have elements that cause the outer periphery to warp from the holding surface. [Explanation of symbols]

[0088] 1: Grinding device 13: Spin cleaning mechanism 14: Chuck Table 15: First conveying mechanism 16: Second conveying mechanism 20: Table movement mechanism 30: Table rotation mechanism 32: Table rotation axis 39: Suction pipe (communication path) 40:Frame body 42: Porous board 44:Communication path 45: Suction source 46: Shut-off valve 47: Pressure gauge 48: Water sealing nozzle 50: Grinding mechanism 56: Grinding Wheel 57: Grinding wheel (machining part) 60: Lifting mechanism 70: Control Unit 71: Suction retention judgment section 72: Leak Judgment Department 73: Control Unit 241: Holding surface 421: Holding surface Pa: Monitoring width Pb: Monitoring width Qa: Moving average Ra: Measured value Rb: Measured value Rc: Measured value Rd: Measured value S: threshold T: Time range W: Work

Claims

1. A suction holding monitoring method is provided in which the holding surface of a chuck table and a suction source are connected by a communication passage, and the holding surface is used to monitor whether it is holding a rectangular workpiece by suction based on the value of a pressure gauge placed in the communication passage. A placement step of placing the workpiece on the holding surface, A suction holding recognition step is performed by connecting the holding surface and the suction source, and recognizing that the holding surface has suction-held the workpiece if the value of the pressure gauge exceeds a preset threshold in the negative pressure direction, and recognizing that the holding surface has not suction-held the workpiece if the value of the pressure gauge does not exceed the threshold in the negative pressure direction. In the suction holding recognition process, a water seal forming step is performed by supplying water to the holding surface which is in communication with the suction source and to the workpiece placed on the holding surface to form a water seal. A suction holding monitoring step is performed, in which, after the water seal is formed, if the pressure gauge reading after it is recognized that the holding surface has suction-held the workpiece fluctuates by a greater than a preset monitoring range, it is recognized that a leak has occurred in the holding surface, and if the fluctuation does not exceed the monitoring range, it is recognized that no leak has occurred in the holding surface. A suction-holding monitoring method comprising the above.

2. The suction holding monitoring method according to Claim 1, wherein, after the water seal is formed, the chuck table is rotated around the center of the holding surface as an axis, and the process is carried out while centrifugal force is applied to the water.

3. The suction holding monitoring method according to claim 1 or claim 2, wherein the monitoring width is the width between the moving average value of the pressure gauge within a preset time range and a value that is moved away from the moving average value in the positive pressure direction.

4. A processing apparatus capable of the suction holding monitoring method described in claim 1, A chuck table that holds a rectangular workpiece on its holding surface, A machining section for machining the workpiece held on the holding surface, A communication passage connecting the holding surface and the suction source, A pressure gauge is placed in the passage and measures the pressure inside the passage. A suction holding determination unit determines that the holding surface is holding the workpiece by suction when the value of the pressure gauge exceeds a preset threshold in the negative pressure direction, A leak detection unit determines that if the pressure gauge value does not exceed a preset monitoring range, there is no leak in the retaining surface, and if the pressure gauge value exceeds a preset monitoring range, there is a leak in the retaining surface. A control unit that stops the device when the leak detection unit determines that a leak has occurred on the holding surface, A processing device equipped with the following features.

5. The processing apparatus according to claim 4, further comprising a water seal nozzle that supplies water to the corners of a workpiece placed on the holding surface, which is in communication with the suction source, to form a water seal.

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