Grinding method for workpieces

Abstract

To provide a workpiece grinding method capable of making a grinding time uniform and short.SOLUTION: A creep feed grinding method for a workpiece W comprises: a coarse grinding step of grinding a top face of the workpiece W by positioning the undersurface of a first grind stone 16 under the top face of the workpiece W by a first distance (100 μm) to relatively horizontally move a first chuck table 3 and the first grind stone 16; and a finish grinding step of grinding the top face of the workpiece W by positioning the undersurface of a second grind stone 16' under the top face of the workpiece W by a second distance (10 μm) to relatively horizontally move a second chuck table 3' and the second grind stone 16'. The method includes a corrective grinding step of grinding the thickness of the workpiece W into a prescribed thickness t0 before the start of the finish grinding step. In the corrective grinding step, the thickness of the workpiece W is made to be a previously set thickness t2 by the corrective grinding of the workpiece W by the difference Δt (=t1-t0) between a thickness t1 of the workpiece W after coarse grinding and the previously set thickness t0.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a grinding method for creep-feed grinding a workpiece to a predetermined thickness.

Background Art

[0002] As a packaging technology for integrating and miniaturizing devices used in various electronic devices, a chip having a device formed thereon is placed on a substrate, a Cu electrode is formed on the chip, and the chip and the Cu electrode are sealed with resin to protect the device from impact, moisture, etc. Then, a technique is known in which the resin is ground to expose the Cu electrode, and further, the resin is ground to obtain a workpiece having a desired thickness.

[0003] And, in a grinding method for grinding a workpiece provided with a Cu electrode to a predetermined thickness, the workpiece is sucked and held by a chuck table, and in a state where the lower surface of a rotating annular grindstone is disposed at a position lowered by a predetermined distance from the upper surface of the workpiece, there is a method of relatively horizontally moving the workpiece and the grindstone to creep-feed grind the upper surface of the workpiece (see, for example, Patent Documents 1 and 2).

[0004] In the above creep-feed grinding, until immediately before the Cu electrode is exposed, rough grinding is performed by repeating, a preset number of times, an operation of grinding the surface of the workpiece by lowering the grindstone, for example, by 100 μm and relatively horizontally moving the grindstone and the workpiece. And after this rough grinding, finish grinding is performed by repeating, until the thickness of the workpiece becomes a preset thickness, an operation of grinding the surface of the workpiece by lowering the grindstone, for example, by 10 μm and relatively horizontally moving the grindstone and the workpiece.

[0005] That is, in rough grinding, an operation of grinding the upper surface of the workpiece, for example, by 100 μm each time is repeated a preset number of times, and in finish grinding, an operation of grinding the upper surface of the workpiece, for example, by 10 μm each time is repeated until the thickness of the workpiece becomes a preset thickness.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-084646 [Patent Document 2] Japanese Patent Publication No. 2020-171977 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In current creep-feed grinding of workpieces, rough grinding of the workpiece is performed only a predetermined number of times. As a result, the thickness of the roughly ground workpiece is not constant, and the time required for subsequent finish grinding varies depending on the thickness of the roughly ground workpiece. In other words, since finish grinding grinds the top surface of the workpiece in increments of, for example, 10 μm, if the thickness of the workpiece after rough grinding is thick, the time required for finish grinding increases, which has the problem of affecting the next process.

[0008] The present invention has been made in view of the above problems, and its purpose is to provide a workpiece grinding method that can standardize the grinding time to a constant and short duration. [Means for solving the problem]

[0009] The present invention, for solving the above problems, is a method for grinding a workpiece in which the lower surface of a grinding wheel is positioned outside the workpiece held on a chuck table and lower than the upper surface of the workpiece, and the upper surface of the workpiece is ground by moving the chuck table and the grinding wheel horizontally relative to each other, wherein the lower surface of a first grinding wheel is positioned a first distance below the upper surface of the workpiece, and the upper surface of the workpiece is ground by moving the chuck table and the first grinding wheel horizontally relative to each other. The process is completed by repeating the rough grinding process a predetermined number of times. The apparatus comprises a rough grinding step and a finish grinding step in which the upper surface of the workpiece is ground by positioning the lower surface of the second grinding wheel at a second distance below the upper surface of the workpiece and moving the chuck table and the second grinding wheel horizontally relative to each other, and is characterized by including a corrective grinding step in which the thickness of the workpiece is ground to a predetermined thickness before starting the finish grinding step. [Effects of the Invention]

[0010] According to the present invention, the workpieces that have been roughly ground in the rough grinding step are corrected in the next corrective grinding step so that their thickness becomes a predetermined thickness. As a result, the thickness of all workpieces before finish grinding becomes constant and predetermined. Therefore, the time required for finish grinding of the workpieces in the next finish grinding step is uniformly short, and the effect is obtained that all workpieces can be ground to a predetermined thickness in a constant short time. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view showing a part of a grinding apparatus for carrying out the workpiece grinding method according to the present invention, in a fractured state. [Figure 2] Figure 1 is a perspective view of the workpiece transport mechanism of the grinding apparatus shown. [Figure 3] This is a flowchart showing the steps of a workpiece grinding method according to the first embodiment of the present invention. [Figure 4] This flowchart shows the procedure for grinding a workpiece according to the first embodiment of the present invention. [Figure 5] (a) and (b) are schematic side views illustrating the rough grinding step in the workpiece grinding method according to the first embodiment of the present invention. [Figure 6] (a) and (b) are schematic side views illustrating the finish grinding step in the workpiece grinding method according to the first embodiment of the present invention. [Figure 7] (a) to (c) are longitudinal cross-sectional views of a workpiece ground by the workpiece grinding method according to the present invention. [Figure 8] This is a flowchart showing the steps of a workpiece grinding method according to the second embodiment of the present invention. [Figure 9] This is a flowchart showing the procedure for a workpiece grinding method according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0012] The embodiments of the present invention will be described below based on the accompanying drawings.

[0013] [Configuration of Grinding Device] First, the configuration of a grinding device for implementing the workpiece grinding method according to the present invention will be described based on FIGS. 1 and 2. In the following description, the arrow directions shown in FIG. 1 are respectively the X-axis direction (left-right direction), the Y-axis direction (front-back direction), and the Z-axis direction (up-down direction).

[0014] The grinding device 1 shown in FIG. 1 is a device for creep feed grinding of a rectangular plate-shaped workpiece W (see FIGS. 5 and 6), and includes a first processing unit U1 for rough grinding the workpiece W and a second processing unit U2 for finish grinding the workpiece W rough-grinded by the first processing unit U1, a first thickness measuring device 5 for measuring the thickness and upper surface height of the workpiece W rough-grinded by the first processing unit U1 and a second thickness measuring device 6 for measuring the thickness of the workpiece W finish-grinded by the second processing unit U2, a temporary placement portion 40 for temporarily placing the workpiece W, workpiece conveying means 20 (see FIG. 2) for conveying the workpiece W between the temporary placement portion 40, the first processing unit U1, and the second processing unit U2, cleaning means 50 for cleaning the workpiece W finish-grinded by the second processing unit U2, a robot 60 for conveying the workpiece W between the first cassette 7 and the alignment table 9 and between the cleaning means 50 and the second cassette 8, and a control unit 70 for controlling the grinding operation of the grinding device 1 as main components.

[0015] Here, before the grinding process, as shown in FIG. 7(a), the workpiece W has a rectangular plate-shaped support substrate W1 made of resin such as a PCB, and a plurality of chips C arranged on the support substrate W1. Devices (not shown) are respectively formed on the surfaces of each chip C. And a plurality of Cu electrodes P respectively project from the surfaces of each device, and these chips C and Cu electrodes P are sealed with a resin F such as an epoxy resin. Each chip C has a base material such as silicon, gallium arsenide, or sapphire.

[0016] Next, the configurations of the first processing unit U1 and the second processing unit U2, which are the main components of the grinding device 1, the first thickness measuring device 5 and the second thickness measuring device 6, the temporary placement unit 40, the workpiece conveying means 20, the cleaning means 50, the robot 60, and the control unit 70 will be described respectively.

[0017] <First Processing Unit and Second Processing Unit> The first processing unit U1 for rough grinding the workpiece W and the second processing unit U2 for finish grinding the workpiece W are arranged side by side along the X-axis direction (left-right direction) on the device base 2 as shown in FIG. 1. Since the basic configurations of these first processing unit U1 and second processing unit U2 are the same, hereinafter, the configuration of the first processing unit U1 will be mainly described.

[0018] The first processing unit U1 includes a first chuck table 3, a rough grinding means 10 as the first processing means, and a first moving mechanism (not shown) for reciprocating the first chuck table 3 in the Y-axis direction. Here, the configurations of the first chuck table 3, the rough grinding means 10, and the first moving mechanism (not shown) that constitute the first processing unit U1 will be described below.

[0019] (First Chuck Table) The first chuck table 3 is a disk-shaped member and can reciprocate along the Y-axis direction by a first moving mechanism (not shown). A circular holding surface 3a for sucking and holding the workpiece W is formed on the upper surface of the first chuck table 3. Note that the holding surface 3a is connected to a suction source (not shown).

[0020] (Rough Grinding Means) The rough grinding means 10 includes a spindle motor 12 fixed to a holder 11, a vertical spindle 13 rotationally driven by the spindle motor 12, a disk-shaped mount 14 attached to the lower end of the spindle 13, and a grinding wheel 15 detachably attached to the lower surface of the mount 14. Here, a plurality of first grinding wheels 16 arranged in an annular shape are attached to the grinding wheel 15.

[0021] The rough grinding means 10 is supported so as to be able to move up and down by a lifting mechanism 30 provided on the -Y axis end face (front surface) of a block-shaped column 4 that is erected vertically at the +Y axis end (rear end) of the device base 2.

[0022] The above-described lifting mechanism 30 moves the rough grinding means 10 up and down along the Z-axis direction (vertical direction), and comprises a rectangular plate-shaped lifting plate 31 and a pair of left and right guide rails 32 for guiding the lifting movement of the lifting plate 31. The rough grinding means 10 is attached to the lifting plate 31. The pair of left and right guide rails 32 are arranged perpendicularly and parallel to each other on the -Y-axis end face (front) of the column 4.

[0023] A rotatable ball screw shaft 33 is positioned vertically along the Z-axis direction (up and down direction) between a pair of left and right guide rails 32, and the upper end of the ball screw shaft 33 is connected to a reversible electric motor 34, which is the drive source. The lower end of the ball screw shaft 33 is rotatably supported by a bearing (not shown) on the column 4, and a nut member (not shown) that protrudes horizontally toward the rear (+Y-axis direction) from the back of the lifting plate 31 is screwed onto this ball screw shaft 33.

[0024] Therefore, when the electric motor 34 of the lifting mechanism 30 configured as described above is activated to rotate the ball screw shaft 33 in both forward and reverse directions, the lifting plate 31, which has a nut member (not shown) protruding from it that screws onto the ball screw shaft 33, moves up and down along a pair of left and right guide rails 32. As a result, the rough grinding means 10 attached to the lifting plate 31 also moves up and down along the Z-axis direction (vertical direction).

[0025] (1st movement mechanism) The first moving mechanism, not shown, reciprocates the first chuck table 3 and the workpiece W held therein along the Y-axis, and is composed of a well-known ball screw mechanism or the like, located within the device base 3. Therefore, further explanation and illustration of this first moving mechanism are omitted.

[0026] The second processing unit U2 includes a second chuck table 3', a second processing means, which is a finish grinding means 10', and a second moving mechanism (not shown). However, the configuration of the second chuck table 3' and the second moving mechanism is the same as that of the first chuck table 3 and the first moving mechanism of the first processing unit U1, so a description of these will be omitted.

[0027] A circular holding surface 3a' for suction holding the workpiece W is formed on the upper surface of the second chuck table 3' of this second processing unit U2.

[0028] Furthermore, the finish grinding means 10', like the rough grinding means 10, includes a spindle motor 12' fixed to a holder 11', a vertical spindle 13' rotationally driven by the spindle motor 12', a disc-shaped mount 14' attached to the lower end of the spindle 13', and a grinding wheel 15' detachably mounted on the lower surface of the mount 14'. Here, the grinding wheel 15' has a plurality of second grinding wheels 16' arranged in an annular shape, and these second grinding wheels 16' are made of finer abrasive grains than the first grinding wheel 16 of the rough grinding means 10. The second processing unit U2 is also provided with a lifting mechanism 30 for raising and lowering the finish grinding means 10'. Since this lifting mechanism 30 is the same as the lifting mechanism 30 for raising and lowering the rough grinding means 10, the same reference numerals are used and further explanation is omitted.

[0029] <First thickness measuring device and second thickness measuring device> (First thickness measuring instrument) The first thickness measuring device 5 serves as both a thickness measuring device for measuring the thickness of the workpiece W being roughly ground by the rough grinding means 10 and a top surface height measuring device for measuring the top surface height of the workpiece W, and is composed of a height gauge. Specifically, this first thickness measuring device 5 is equipped with a first contact element 5a that contacts the top surface of the workpiece W held on the first chuck table 3 and a second contact element 5b that contacts the outer peripheral top surface of the first chuck table 3. With this first thickness measuring device 5, the top surface height of the workpiece W is measured by the first contact element 5a, and the thickness of the workpiece W during rough grinding is determined by subtracting the top surface height of the first chuck table 3 measured by the second contact element 5b from the top surface height of the workpiece W measured by the first contact element 5a.

[0030] (Second thickness measuring instrument) The second thickness measuring instrument 6 measures the thickness of the workpiece W being finished grinding by the finish grinding means 10', and, like the first thickness measuring instrument 5, is composed of a height gauge. Specifically, this second thickness measuring instrument 6 is equipped with a first contact element 6a that contacts the upper surface of the workpiece W held by the second chuck table 3', and a second contact element 6b that contacts the upper surface of the outer periphery of the second chuck table 3'. With this second thickness measuring instrument 6, the thickness of the workpiece W during finish grinding can be determined by subtracting the height of the upper surface of the second chuck table 3' measured by the second contact element 6b from the height of the upper surface of the workpiece W measured by the first contact element 6a.

[0031] <Temporary placement section> The temporary storage section 40 is for temporarily storing the workpiece W that has been roughly ground by the rough grinding means 10 of the first processing unit U1, in order to transfer it to the second processing unit U2. As shown in Figure 1, it is located in the Y-axis direction between the first processing unit U1 and the second processing unit U2 on the device base 2 and the first cassette 7 and the second cassette 8.

[0032] The temporary storage section 40 includes a temporary storage table 43 that is movable in the X-axis direction along a guide plate 42 laid along the X-axis direction on a horizontal temporary storage base 41. The upper surface of the temporary storage table 43 has a circular holding surface 43a for suction holding the workpiece W. Although not shown, the temporary storage section 40 is provided with a moving mechanism that moves the temporary storage table 43 along the guide plate 42 in the X-axis direction.

[0033] <Workpiece transport means> The workpiece transport means 20 shown in Figure 2 is located in spaces S1 and S2, respectively, indicated by dashed lines in Figure 1, and the configuration of both is the same.

[0034] This workpiece transport means 20 holds a workpiece W and transports it to a predetermined position, and as shown in Figure 2, it is equipped with a pair of rectangular plate-shaped transport pads 21 that suction-hold the workpiece W. The pair of transport pads 21 are mounted parallel to each other on a reversing mechanism 22 that intermittently rotates them by 180°, and the reversing mechanism 22 is mounted on the tip of a rotating shaft 24 that extends horizontally from a block-shaped lifting block 23. Multiple suction cups 25 are attached to the suction surface of each transport pad 21.

[0035] The transport pad 21 is movable in the Y-axis direction (forward and backward direction) by the Y-axis movement mechanism 20A, and is also movable up and down in the Z-axis direction by the Z-axis movement mechanism 20B. The Y-axis movement mechanism 20A includes a pair of upper and lower guide rails 22a arranged parallel to each other along the Y-axis direction on the side surface of the base plate 21a, and a slider 23a that can slide along these guide rails 22a in the Y-axis direction. A rotatable ball screw shaft 24a extending along the Y-axis direction is positioned between the pair of guide rails 22a.

[0036] One axial end of the ball screw shaft 24a is connected to an electric motor 25a, which is the drive source, and the other axial end of the ball screw shaft 24a is rotatably supported on a base plate 21a by a bearing 26a. The ball screw shaft 24a is then screwed into a rectangular block-shaped slider 23a.

[0037] The Z-axis movement mechanism 20B includes a guide rail 22b mounted perpendicularly along the Z-axis direction to a base plate 21b attached to the side of the slider 23a, and a lifting block 23b that moves up and down along the guide rail 22b in the Z-axis direction. From the lifting block 23b, the rotating shaft 24 that supports the first transport pad 21 via a reversing mechanism 22 at its tip extends horizontally along the +X-axis direction, and a vertically positioned rotatable ball screw shaft 24b is screwed into the lifting block 23b. The upper end of the ball screw shaft 24b is connected to an electric motor 25b, which is a rotation drive source, and the lower end of the ball screw shaft 24b is rotatably supported on the base plate 21b by a bearing 26b.

[0038] Therefore, when the electric motor 25a of the Y-axis movement mechanism 20A is activated to rotate the ball screw shaft 24a in both forward and reverse directions, the slider 23a, which is screwed onto the ball screw shaft 24a, moves along the guide rail 22a in the Y-axis direction together with the Z-axis movement mechanism 20B. When the electric motor 25b of the Z-axis movement mechanism 20B is activated to rotate the ball screw shaft 24b in both forward and reverse directions, the lifting block 23b, which is screwed onto the ball screw shaft 24b, moves up and down along the Z-axis direction. As a result, the transport pad 21, which is supported by the lifting block 23b via the rotating shaft 24 and the reversing mechanism 22, can move in the Y-axis direction and also move up and down in the Z-axis direction.

[0039] Although not shown in the figures, the grinding apparatus 1 according to this embodiment is provided with a grinding water supply means that supplies grinding water, which is a processing fluid, to the first grinding wheel 16 of the rough grinding means 10 and the second grinding wheel 16' of the finish grinding means 10' during the grinding process. This grinding water supply means supplies grinding water to the first grinding wheel 16 and the second grinding wheel 16' of each grinding wheel 15, 15' through the axial centers of the respective spindle motors 12, 12' and spindles 13, 13' of the rough grinding means 10 and the finish grinding means 10', respectively, and the contact surfaces between the first grinding wheel 16 and the second grinding wheel 16' and the workpiece W are cooled by the grinding water. Here, pure water is preferably used as the grinding water.

[0040] <Cleaning methods> The cleaning means 50 cleans the workpiece W, which has been finish-ground by the finish grinding means 10' of the second processing unit U2, with cleaning water, and is positioned below the temporary storage section 40 in the Y-axis direction, as shown in Figure 1. This cleaning means 50 includes a spinner table 51 that holds the finish-ground workpiece W by suction to its upper surface and rotates at a predetermined speed around a vertical central axis, and a cleaning water nozzle 52 that sprays cleaning water toward the workpiece W held by the spinner table 51. Pure water is preferably used as the cleaning water.

[0041] <Robot> The robot 60 is an articulated robot that has the function of taking out the workpiece W before grinding, which is stored in the first cassette 7, and transporting it to the alignment table 9, and transporting the workpiece W, which has been cleaned in the cleaning means 50, to the second cassette 8 and storing it in the second cassette 8.

[0042] In this robot 60, a robot hand 61 for suction and holding a workpiece W is detachably attached to a mounting section 62. The robot 60 is also provided with a horizontal movement mechanism 63 for moving the robot hand 61 horizontally and a lifting mechanism 64 for raising and lowering the robot hand 61. The horizontal movement mechanism 63 comprises a bendable first arm 63a and a second arm 63b, with the lifting mechanism 64 connected to one end of the first arm 63a.

[0043] <Department Head> The control unit 70 shown in Figure 1 includes a CPU (Central Processing Unit) that performs calculations according to a control program, and memory such as ROM (Read Only Memory) and RAM (Random Access Memory). This control unit 70 has the function of controlling the operation of the grinding device 1 so that the workpiece W is ground to a predetermined thickness through rough grinding by the first processing unit U1 and finish grinding by the second processing unit U2, as will be described later. Details of this will be described later.

[0044] [Workpiece grinding method] Next, a first embodiment of the grinding method for a workpiece W according to the present invention, which is performed in the grinding apparatus 1 configured as described above, will be explained.

[0045] <First Embodiment> As shown in Figure 3, the grinding method according to the first embodiment grinds the workpiece W to a predetermined thickness through 1) a rough grinding step, 2) a compensatory grinding step, and 3) a finish grinding step. In the 2) compensatory grinding step, 2-1) a thickness measurement step, 2-2) a calculation step, and 2-3) a thickness compensatory grinding step are performed in this order. Each step will be described below.

[0046] 1) Rough grinding process: In the rough grinding process, the robot 60 shown in Figure 1 takes one workpiece W from the first cassette 7 before grinding and sets it on the alignment table 9. The workpiece W is then aligned on the alignment table 9, and the aligned workpiece W is held by suction on the transport pad 21 of the workpiece transport means 20 shown in Figure 2 and transferred to the first chuck table 3 of the first processing unit U1, where it is held by suction on the holding surface 3a of the first chuck table 3.

[0047] The first chuck table 3, which holds the workpiece W by suction, waits at the rough grinding start position Y1 shown in Figure 5(a). At this time, the control unit 70 sets the number of rough grinding cycles n to 0 (n=0) as an initial setting (step S1 in Figure 4). The control unit 70 also drives the lifting mechanism 30 of the first processing unit U1 to position the first grinding wheel 16 of the rough grinding means 10 so that its lower surface is below the surface of the workpiece W by a first distance (100 μm in this embodiment) (step S2 in Figure 4).

[0048] From the above state, the control unit 70 starts the spindle motor 12 of the rough grinding means 10 to rotate the first grinding wheel 16 around its central axis at a predetermined speed, and drives the first moving mechanism (not shown) to move the first chuck table 3 together with the workpiece W held therein from the rough grinding start position Y1 shown in Figure 5(a) to the rough grinding end position Y2 shown in Figure 5(b) at a predetermined speed in the direction of arrow a. As a result, the surface (resin F) of the workpiece W is roughly ground by creep feed grinding by the first grinding wheel 16 to a thickness of 100 μm (step S3 in Figure 4). When this rough grinding is completed, the first chuck table 3 and the workpiece W are moved from the rough grinding end position Y2 in the direction of arrow b shown by the first moving mechanism (not shown) to return to the rough grinding start position Y1.

[0049] As described above, when the upper surface of the workpiece W is roughly ground to a thickness of 100 μm in one rough grinding pass, the control unit 70 counts the number of rough grinding passes n and sets n=1 (step S4 in Figure 4). In this embodiment, since the number of rough grinding passes n is set to 3 (i.e., rough grinding is performed only 3 times), the control unit 70 determines whether the counted number of rough grinding passes n has reached 3 (step S5), and if the counted number of rough grinding passes n has not reached 3 (step S5: No), the above rough grinding is repeated (steps S2 to S5).

[0050] When the rough grinding of the workpiece W is performed three times (Step S5: Yes in FIG. 4), as shown in FIG. 7(a), the surface of the workpiece W (resin F) is rough-grinded by 300 μm, and the thickness of the workpiece W becomes t1 shown in the figure. Next, a correction grinding process is performed. In the present embodiment, the grinding allowance for one rough grinding is set to 100 μm, and the number of rough grinding times n is set to 3. However, these grinding allowances and the number of rough grinding times n can be set to arbitrary values.

[0051] 2) Thickness correction grinding process: As described above, in the thickness correction grinding process, the 2-1) thickness measurement process, 2-2) calculation process, and 2-3) thickness correction grinding process described below are performed in this order (see FIG. 3).

[0052] 2-1) Thickness measurement process: In the thickness measurement process, the thickness t1 of the workpiece W rough-grinded in the 1) rough grinding process described above (see FIG. 5(a)) is measured by the first thickness measuring instrument 5 shown in FIG. 1 (Step S6 in FIG. 4).

[0053] 2-2) Calculation process: In the calculation process, the difference (thickness difference) Δt (= t1 - t0) (see FIG. 5(a)) between the thickness t1 of the workpiece W measured by the first thickness measuring instrument 5 shown in FIG. 1 and the preset thickness t0 (<t1) is calculated (Step S7 in FIG. 4). Note that the thickness difference calculated in this calculation process is the consumption amount of the first grinding wheel 16.

[0054] 2-3) Thickness correction grinding process: In the thickness correction grinding process, the first grinding wheel 16 is lowered so that the lower surface of the first grinding wheel 16 is positioned Δt below the surface of the workpiece W rough-grinded (Step S8 in FIG. 4). Similar to the rough grinding (see FIG. 5), the first chuck table 3 and the workpiece W are moved in the Y-axis direction by a first moving mechanism (not shown), and the surface of the workpiece W (resin F) is subjected to thickness correction grinding with a grinding allowance of Δt (Step S9 in FIG. 4). Then, as shown in FIG. 5(b), a workpiece W with a preset predetermined thickness t0 is obtained. In this state, the Cu electrode P is not exposed from the surface of the workpiece W and is buried inside the resin F.

[0055] Here, the relationship t1 - Δt = t0 holds between the thickness t1 of the workpiece W after rough grinding, the grinding allowance Δt of the workpiece W in the thickness correction grinding process, and the thickness t0 of the workpiece W after thickness correction grinding.

[0056] 3) Finish grinding process: Once a workpiece W with a predetermined thickness t0 is obtained in the rough grinding process described above, the workpiece W is transported to the temporary storage section 40 shown in Figure 1 by the workpiece transport means (first workpiece transport means) 20 shown in Figure 2, which is located in the space S1 shown in Figure 1. The workpiece W with the thickness corrected by grinding to a thickness t0 is then placed and held on the temporary storage table 43 in the temporary storage section 40, and the temporary storage table 43 holding the workpiece W moves in the -X axis direction along the guide plate 42 by a moving mechanism (not shown).

[0057] Next, the workpiece W is transported to the second chuck table 3' of the second processing unit U2 by the workpiece transport means (second workpiece transport means) 20 shown in Figure 2, which is located in space S2 in Figure 1, and the workpiece W is held by suction on the holding surface 3a' of the second chuck table 3'.

[0058] As described above, the second chuck table 3', which holds the workpiece W by suction, waits at the finish grinding start position Y3 shown in Figure 6(a). At this time, the control unit 70 drives the lifting mechanism 30 of the second processing unit U2, and as shown in Figure 6(a), positions the second grinding wheel 16' of the finish grinding means 10' so that its lower surface is below the surface of the workpiece W by a second distance (10 μm in this embodiment) (step S10 in Figure 4).

[0059] From the above state, the control unit 70 activates the spindle motor 12' of the finishing grinding means 10' to rotate the second grinding wheel 16' around its central axis at a predetermined speed, and simultaneously drives a second moving mechanism (not shown) to move the second chuck table 3' together with the workpiece W held therein from the finishing grinding start position Y3 shown in Figure 6(a) to the finishing grinding end position Y4 shown in Figure 6(b) at a predetermined speed in the direction of arrow c. As a result, the surface (resin F) of the workpiece W is finished grinded by the second grinding wheel 16' to a thickness of 10 μm (step S11 in Figure 4). When this finishing grinding is completed, the second chuck table 3' and the workpiece W are moved from the finishing grinding end position Y4 in the direction of arrow d by the second moving mechanism (not shown) back to the finishing grinding start position Y3.

[0060] As described above, once the upper surface of the workpiece W is finished by a thickness of 10 μm in a single finish grinding, the thickness of the workpiece W is measured by the second thickness measuring instrument 6 shown in Figure 1 (step S12 in Figure 4), and the result is transmitted to the control unit 70. The control unit 70 then determines whether the measured thickness of the workpiece W has reached a predetermined thickness t2 (see Figures 7(b) and (c)) (step S13 in Figure 4).

[0061] If the measured thickness of the workpiece W is greater than a predetermined thickness t2 (step S13: No), the operations in steps S10 to S13 are repeated until the measured thickness of the workpiece W becomes equal to the predetermined thickness t2, and the finish grinding of the workpiece W is repeated multiple times. In this embodiment, as shown in Figure 7(b), the finish grinding is repeated 5 times to obtain a workpiece W with the predetermined thickness t2 shown in Figure 7(c). Note that the number of finish grinding cycles is determined by the amount of grinding per cycle and is not limited to 5 cycles.

[0062] Then, in the workpiece W with a predetermined thickness t2 that has been finished grinding, as shown in Figure 7(c), the Cu electrode P is also ground down and a portion of it is exposed from the surface of the workpiece W.

[0063] As described above, according to the grinding method for workpieces W of the present invention, the workpieces W that have been roughly ground in the rough grinding step are corrected in the next corrective grinding step so that their thickness becomes a predetermined thickness t0. Therefore, the thickness of all workpieces W before finish grinding becomes constant at the predetermined thickness t0. Consequently, the time required for finish grinding of the workpieces W in the next finish grinding step is uniformly short, and all workpieces W can be ground to a predetermined thickness t2 in a constant short time.

[0064] Once the finish grinding of the workpiece W in the second processing unit U2 is completed as described above, the finished grinding workpiece W is held by the workpiece transport means 20 shown in Figure 2, which is located in the space S2 in Figure 1, and transported to the cleaning means 50, where it is handed over to the spinner table 51 of the cleaning means 50.

[0065] In the cleaning means 50, the spinner table 51 is rotated at a predetermined speed around a vertical central axis by a rotation mechanism (not shown) together with the workpiece W, and cleaning water is sprayed from the cleaning water nozzle 52 toward the workpiece W. As a result, the workpiece W is cleaned by the cleaning water, and grinding debris adhering to the surface of the workpiece W is removed. The workpiece W, cleaned in this way by the cleaning means 50, is held by the robot 60 and transported to the second cassette 8, where it is stored, and the series of grinding operations on one workpiece W is completed.

[0066] <Second Embodiment> Next, a second embodiment of the workpiece grinding method according to the present invention will be described below with reference to Figures 8 and 9.

[0067] In the grinding method according to this embodiment, as shown in Figure 8, the workpiece W is ground through 1) a rough grinding step, 2) a compensatory grinding step, and 3) a finish grinding step, similar to the first embodiment, except that the method for setting the compensatory grinding amount in 2) the compensatory grinding step differs from that of the first embodiment. Therefore, in the following, only 2) the compensatory grinding step will be described, and the explanations of 1) the rough grinding step and 3) the finish grinding step will be omitted. Also, in the flowchart shown in Figure 9, the same processes as in the flowchart shown in Figure 4 are denoted by the same reference numerals as the steps shown in Figure 4.

[0068] 2) Corrective grinding process: In the corrective grinding process, as shown in Figure 8, the following steps are performed in this order: 2-1) top surface height measurement step, 2-2) calculation step, and 2-3) top surface height corrective grinding step.

[0069] 2-1) Top surface height measurement process: In the top surface measurement process, 1) the top surface height h1 (see Figure 7(a)) of the workpiece W that has been roughly ground in the rough grinding process is measured by the first thickness measuring instrument 5 shown in Figure 1 (step S6' in Figure 9).

[0070] 2-2) Calculation process: In the calculation process, the upper surface height h1 of the workpiece W measured by the first thickness measuring instrument 5 shown in Figure 1 and the height h2 (which is a predetermined thickness t3 above the holding surface 3a of the first chuck table 3) are used.

[0071] 2-3) Top surface height correction grinding process: ​In the upper surface height correction grinding process, the first grinding wheel 16 is lowered so that its lower surface is located below the surface of the roughly ground workpiece W by a height difference Δh (step S8' in Figure 9). Then, as in the rough grinding process (see Figure 5), the first chuck table 3 and the workpiece W are moved in the Y-axis direction by a first moving mechanism (not shown), and the surface of the workpiece W (resin F) is thickness-corrected by grinding with a grinding allowance Δh (step S9 in Figure 9). As a result, a workpiece W with a predetermined thickness t0 is obtained, as shown in Figure 7(b).

[0072] Thereafter, as in the first embodiment, the workpiece W is finish-ground (steps S10 to S14 in Figure 9), and the workpiece W is ground to a predetermined thickness t2 (see Figure 7(c)).

[0073] In this embodiment as well, similar to the first embodiment, the workpiece W that has been roughly ground in the rough grinding step is corrected in the next corrective grinding step so that its thickness becomes a predetermined thickness t0. As a result, the thickness of the workpiece W before finish grinding is constant for all workpieces W, which is the predetermined thickness t0. Therefore, the time required for finish grinding of the workpiece W in the next finish grinding step is uniformly short, and the effect is obtained that all workpieces W can be ground to a predetermined thickness t2 in a constant short time.

[0074] In the above embodiment, creep feed grinding was performed by moving the first and second chuck tables 3,3' (workpiece W) relative to the fixed first and second grinding wheels 16,16'. However, the opposite may be performed, where the first and second grinding wheels 16,16' are moved relative to the first and second chuck tables 3,3' (workpiece W).

[0075] Alternatively, creep feed grinding may be performed each time the first and second chuck tables 3,3' and the first and second grinding wheels 16,16' move back and forth relative to each other.

[0076] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the technical idea described in the claims, specification, and drawings. [Explanation of Symbols]

[0077] 1: Grinding device, 2: Device base, 3: First chuck table, 3a: Holding surface, 3': Second chuck table, 3a': Holding surface, 4: Column, 5: First thickness measuring instrument (thickness measuring instrument, top surface height measuring instrument, 5a: First contact element, 5b: Second contact element, 6: Second thickness measuring instrument, 6a: First contact element, 6b: Second contact element, 7: First cassette, 8: Second cassette, 9: Alignment table, 10: Rough grinding means, 11,11': Holder, 12,12': Spindle motor, 13,13': Spindle, 14,14': Mount, 15,15': Grinding wheel, 16: First grinding wheel, 16': Second grinding wheel, 20: Workpiece transport means, 20A: Y-axis movement mechanism, 20B: Z-axis movement mechanism, 21: Conveyor pad (second conveyor pad), 21a, 21b: Base plate, 22a, 22b: Guide rail, 23a: Slider, 23b: Lifting block, 24a, 24b: Ball screw shaft, 25a, 25b: Electric motor, 26a, 26b: Bearings, 25: Suction cups, 30: Lifting mechanism, 31: Lifting plate, 32: Guide rail, 33: Ball screw shaft, 34: Electric motor, 40: Temporary storage section, 41: Temporary stand, 42: Guide plate, 43: Temporary table, 43a: Holding surface, 50: Washing means, 51: Spinner table, 52: Washing water nozzle, 60: Robot, 61: Robot hand, 62: Mounting part, 63: Horizontal movement mechanism, 63a: First arm, 63b: Second arm, 64: Lifting mechanism, 70: Control unit, C: Chip, F: Resin, h1: Height of the top surface of the roughly ground workpiece. h2: Height above a predetermined thickness from the holding surface, P: Cu electrode, S1, S2: Space, t0: Pre-set workpiece thickness, t1: Thickness of roughly ground workpiece, t2: predetermined thickness of the workpiece after finish grinding, t3: preset thickness, Δt: thickness difference, Δh: height difference, U1: first processing unit, U2: second processing unit, W: workpiece W1: Support substrate, Y1: Rough grinding start position, Y2: Rough grinding end position Y3: Start position for finish grinding, Y4: End position for finish grinding

Claims

1. A method for grinding a workpiece, comprising positioning the lower surface of a grinding wheel at a position lower than the upper surface of the workpiece outside the workpiece held on a chuck table, and grinding the upper surface of the workpiece by moving the chuck table and the grinding wheel horizontally relative to each other, A rough grinding process is completed by repeating a pre-set number of times a rough grinding operation in which the upper surface of the workpiece is ground by positioning the lower surface of the first grinding wheel at a first distance below the upper surface of the workpiece and moving the chuck table and the first grinding wheel horizontally relative to each other, and A finishing grinding process in which the upper surface of the workpiece is ground by positioning the lower surface of the second grinding wheel at a second distance below the upper surface of the workpiece and moving the chuck table and the second grinding wheel horizontally relative to each other, Equipped with, A method for grinding a workpiece, comprising a compensatory grinding step of grinding the thickness of the workpiece to a predetermined thickness before starting the finish grinding step.

2. The corrective grinding process is, A thickness measurement step in which the thickness of the workpiece held on the chuck table is measured with a thickness measuring instrument, A calculation step for calculating the difference between the thickness measured in the thickness measurement step and a preset thickness, A method for grinding a workpiece according to claim 1, comprising: a thickness correction grinding step, in which the lower surface of the first grinding wheel is positioned below the upper surface of the workpiece ground in the rough grinding step by the difference calculated in the calculation step, and the upper surface of the workpiece is ground by relatively moving the chuck table and the first grinding wheel horizontally.

3. The corrective grinding process is, A top surface height measurement step in which the top surface height of a workpiece held on the chuck table is measured using a top surface height measuring instrument, A calculation step which calculates the difference between the upper surface height of the workpiece measured in the upper surface height measurement step and the height above the holding surface for holding the workpiece on the chuck table by a predetermined thickness, A method for grinding a workpiece according to claim 1, comprising: a top surface height correction grinding step, in which the lower surface of the first grinding wheel is positioned below the top surface of the workpiece ground in the rough grinding step by the difference calculated in the calculation step, and the top surface of the workpiece is ground by relatively moving the chuck table and the first grinding wheel horizontally.

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