Method for grinding a workpiece

Abstract

The present invention provides a workpiece grinding method capable of preventing excessive consumption of a grinding tool and also capable of achieving reduction of grinding load. The workpiece grinding method is a grinding method for thinning a workpiece to a finished thickness using a grinding device, and includes a first grinding step of grinding the workpiece to a predetermined thickness while supplying grinding water capable of suppressing consumption of the grinding tool, and a second grinding step of grinding the workpiece to the finished thickness while supplying grinding water of a second grinding water amount that is lower than the first grinding water amount and increases consumption of the grinding tool to promote self-sharpening, after the first grinding step is performed, and promoting sharpening of the grinding tool to prepare for processing of a next workpiece.

Description

Technical Field

[0001] This invention relates to a grinding method for a workpiece. Background Technology

[0002] Grinding apparatuses for thinning workpieces such as wafers on which semiconductor devices are formed have been used for a long time (see, for example, Patent Documents 1 and 2). The above-mentioned grinding apparatuses have the following problems: when grinding hard substrates such as silicon carbide (SiC) or sapphire, especially at the beginning of processing, the grinding wheel has difficulty gripping the workpiece, the grinding load increases, and the spindle current value tends to rise.

[0003] Therefore, in grinding equipment, reducing the amount of grinding water increases the consumption of grinding wheels, promotes spontaneous sharpening, and thus reduces the grinding load. However, when the grinding equipment continuously processes multiple sheets, the increased consumption of grinding wheels leads to increased costs and a higher frequency of grinding wheel replacements, making it less desirable.

[0004] In addition, a grinding device that makes it easier for the grinding wheel to bite by reducing the amount of grinding water at the start of processing has been proposed (see, for example, Patent Document 3).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-24041

[0006] Patent Document 2: Japanese Patent Application Publication No. 2017-56523

[0007] Patent Document 3: Japanese Patent Application Publication No. 2014-124690

[0008] However, in cases where the workpiece has been ground smooth due to previous workpiece processing, there is concern that even if the amount of grinding water is reduced at the start of the process when the grinding load is most easily applied, the grinding wheel will have difficulty gripping the workpiece, the grinding load will increase, and the increase in spindle current value cannot be suppressed. Summary of the Invention

[0009] Therefore, the object of the present invention is to provide a grinding method for a workpiece that can prevent excessive wear of the grinding tool and reduce the grinding load.

[0010] According to the present invention, a grinding method for a workpiece is provided, wherein a grinding apparatus is used to thin the workpiece to a finished thickness. The grinding apparatus comprises: a holding table for holding the workpiece; a grinding unit having a spindle for mounting a grinding wheel and an electric motor for rotating the spindle, wherein a grinding wheel is annularly arranged with a grinding tool for grinding the workpiece held by the holding table; a grinding feed unit for moving the grinding unit away from and towards the holding table; a grinding water supply unit for supplying grinding water to the upper surface of the workpiece held by the holding table in a flow rate adjustable manner; and a control unit for controlling... Each of the aforementioned units is controlled, wherein the grinding method for the workpiece includes the following steps: a first grinding step in which grinding water of a first amount capable of suppressing the consumption of the grinding wheel is provided while the grinding unit is fed to grind the workpiece to a predetermined thickness; and a second grinding step in which, after the first grinding step is performed, grinding water of a second amount lower than the first amount of grinding water and increasing the consumption of the grinding wheel to promote spontaneous sharpening is provided while the grinding unit is fed to grind the workpiece to a finished thickness, thereby promoting the sharpening of the grinding wheel and preparing for the next workpiece to be processed.

[0011] Preferably, the grinding unit includes: a rough grinding unit that uses coarse-grit grinding wheels; and a fine grinding unit that uses fine-grit grinding wheels to grind the workpiece that has been ground by the rough grinding unit, wherein the first grinding step and the second grinding step are performed in the rough grinding unit.

[0012] The grinding method for the workpiece of the present invention has the following effects: it can prevent excessive consumption of grinding tools and reduce grinding load. Attached Figure Description

[0013] Figure 1 This is a perspective view showing an example of the structure of a grinding apparatus used in the grinding method for the workpiece in the embodiment.

[0014] Figure 2 This is a perspective view of the workpiece being processed in the grinding method of the workpiece as an embodiment.

[0015] Figure 3 It is shown schematically. Figure 1 A cross-sectional view of the structure of the grinding unit, the holding table, and the grinding water supply unit of the grinding apparatus shown.

[0016] Figure 4 This is a flowchart illustrating the process of a grinding method for a workpiece according to an embodiment.

[0017] Figure 5 It is shown Figure 4 The graph shows the changes in the amount of grinding water and the spindle current value in the grinding method for the workpiece shown.

[0018] Figure 6 This is a graph showing the changes in the amount of grinding water and the spindle current value in Comparative Example 1.

[0019] Figure 7 This is a graph showing the changes in the amount of grinding water and the spindle current value in Comparative Example 2.

[0020] Label Explanation

[0021] 1: Grinding device; 3: Rough grinding unit; 4: Fine grinding unit; 5: Grinding feed unit; 7: Holding table; 14: Grinding water supply unit; 31, 41: Grinding tool; 32, 42: Grinding wheel; 33: Spindle; 34: Motor; 100: Control unit; 200: Workpiece; 205: Back side (upper surface of the workpiece); 206: Finished thickness; 401: First grinding water volume; 402: Second grinding water volume; 1001: First grinding step; 1002: Second grinding step. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the constituent elements described below include contents that are readily conceived by those skilled in the art and substantially the same. Additionally, the structures described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications to the structure can be made without departing from the spirit of the present invention.

[0023] The grinding method for a workpiece according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a perspective view showing an example of the structure of a grinding apparatus used in the grinding method for the workpiece in the embodiment. Figure 2 This is a perspective view of the workpiece being processed in the grinding method of the embodiment. Figure 3 It is shown schematically. Figure 1 A cross-sectional view of the structure of the grinding unit, the holding table, and the grinding water supply unit of the grinding apparatus shown. Figure 4 This is a flowchart illustrating the process of a grinding method for a workpiece according to an embodiment. Figure 5 It is shown Figure 4 The graph shows the changes in the amount of grinding water and the spindle current value in the grinding method for the workpiece shown.

[0024] The grinding method for the workpiece in the embodiment uses Figure 1 The grinding device 1 pair shown Figure 2The method illustrates a grinding process for thinning the workpiece 200. The workpiece 200, as described in this embodiment, is a disc-shaped semiconductor wafer with silicon as its substrate 201, or an optical device wafer with sapphire, SiC (silicon carbide), or the like as its substrate 201. In this embodiment, the disc-shaped substrate 201 of the workpiece 200 is formed of a material harder than silicon, such as sapphire or SiC (silicon carbide).

[0025] like Figure 2 As shown, the workpiece 200 has devices 204 formed in multiple regions on the front side 202 of the substrate 201, divided by multiple intersecting (perpendicular in the embodiment) predetermined dividing lines 203. The devices 204 are, for example, integrated circuits such as IC (Integrated Circuit) or LSI (Large Scale Integration), image sensors such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), or MEMS (Micro Electromechanical Systems). For the workpiece 200, a protective member 210 is attached to the front side 202 of the substrate 201, and the front side 202 is held on the holding surface 71 by the protective member 210. The back side 205 of the back side of the front side 202 is then ground.

[0026] Next, the grinding method used in the embodiment of the workpiece is described. Figure 1 The grinding apparatus 1 shown will be described below. Grinding apparatus 1 is a processing apparatus for grinding the back surface 205 of a workpiece 200. For example... Figure 2 As shown, the grinding device 1 mainly includes: device body 2, rough grinding unit 3 (equivalent to grinding unit), fine grinding unit 4 (equivalent to grinding unit), grinding feed unit 5, rotary table 6, multiple (three in the embodiment) holding worktables 7, boxes 8 and 9 arranged on the rotary table 6, alignment unit 10, conveying unit 11, cleaning unit 12, loading and unloading unit 13, and control unit 100.

[0027] The rotary table 6 is a disc-shaped worktable mounted on the upper surface of the main body 2, configured to rotate in the horizontal plane and driven to rotate at predetermined times. For example, three holding worktables 7 are arranged on the rotary table 6 at equal intervals with a phase angle of 120 degrees. These three holding worktables 7 are constructed with vacuum chucks that connect the holding surface 71 to the suction source 72. The workpiece 200 is placed on the holding surface 71 and held in place by suction. During grinding, these holding worktables 7 are driven to rotate in the horizontal plane about an axis parallel to the vertical direction, i.e., the Z-axis, via a rotary drive mechanism. Thus, the holding worktables 7, with the holding surface 71 holding the workpiece 200, are capable of rotating about the axis.

[0028] The worktable 7 is moved sequentially to the loading / unloading area 301, the rough grinding area 302, the fine grinding area 303, and the loading / unloading area 301 by the rotation of the turntable 6.

[0029] In addition, the loading and unloading area 301 is the area where the workpiece 200 is loaded and unloaded relative to the holding table 7, the rough grinding area 302 is the area where the workpiece 200 held by the holding table 7 is rough ground (equivalent to grinding) using the rough grinding unit 3, and the fine grinding area 303 is the area where the workpiece 200 held by the holding table 7 is fine ground (equivalent to grinding) using the fine grinding unit 4.

[0030] The rough grinding unit 3 is a grinding unit equipped with a rough grinding wheel 32 arranged in a ring for rough grinding of the workpiece 200 held by the holding table 7, and for rough grinding of the back surface 205 of the workpiece 200 held by the holding surface 71 of the holding table 7 in the rough grinding area 302. The fine grinding unit 4 is a grinding unit equipped with a fine grinding wheel 42 arranged in a ring for fine grinding of the workpiece 200 held by the holding table 7, and for fine grinding of the back surface 205 of the workpiece 200 held by the holding surface 71 of the holding table 7 in the fine grinding area 303.

[0031] Therefore, the rough grinding unit 3 is a grinding unit that uses the grinding wheel 32 for rough grinding, and the fine grinding unit 4 is a grinding unit that uses the grinding wheel 42 to perform fine grinding on the workpiece 200 that has undergone rough grinding in the rough grinding unit 3. In addition, the structures of grinding units 3 and 4 are roughly the same, so the same reference numerals will be used to describe the same parts below.

[0032] like Figure 1As shown, the rough grinding unit 3 and the fine grinding unit 4 have a spindle 33 with grinding wheels 32 and 42 mounted at its lower end, and a motor 34 that drives the spindle 33 to rotate about an axis parallel to the vertical direction (also known as the Z-axis direction). Figure 3 As shown, grinding wheels 32 and 42 have annular bases 35 and multiple grinding tools 31 and 41 fixed to the lower surface of the annular bases 35. The grinding tools 31 and 41 are arranged circumferentially on the outer edge of the lower surface of the annular bases 35. The grinding tools 31 and 41 are formed by fixing abrasive grains with a bonding agent. Compared to the abrasive grains of the grinding tools 41 of the grinding wheel 42, the abrasive grains of the grinding tools 31 of the grinding wheel 32 have a coarser grain size (i.e., larger abrasive grains), while the abrasive grains of the grinding tools 41 of the grinding wheel 42 have a finer grain size.

[0033] The spindle 33 is rotatably housed within the spindle housing 36 about an axis parallel to the Z-axis direction perpendicular to the retaining surface 71, and is rotated about this axis by a motor 34 mounted in the spindle housing 36. The spindle 33 is cylindrical, as shown in the image. Figure 3 As shown, a grinding wheel mounting base 37 for mounting grinding wheels 32 and 42 is provided at the lower end. The grinding wheel mounting base 37 protrudes outward from the lower end of the spindle 33 along its entire circumference, and the outer circumferential surface is circular. The upper surface of the annular base 35 overlaps the lower surface of the grinding wheel mounting base 37, and the grinding wheels 32 and 42 are fixed by bolts (not shown). The spindle 33 and the grinding wheel mounting base 37 are arranged coaxially with each other.

[0034] The grinding units 3 and 4 rotate the spindle 33 and grinding wheels 32 and 42 around the axis via the motor 34 and supply grinding water to the back surface 205 of the workpiece 200 held by the holding table 7 in the grinding areas 302 and 303. Meanwhile, the grinding feed unit 5 brings the grinding tools 31 and 41 close to the holding table 7 at a specified feed speed, thereby performing rough grinding or fine grinding on the back surface 205 of the workpiece 200.

[0035] Furthermore, in this embodiment, grinding units 3 and 4 are equipped with a current value measuring sensor 38 that measures the current value (hereinafter referred to as the spindle current value) flowing in the motor 34 when the spindle 33 rotates around its axis. The current value measuring sensor 38 outputs the measurement result to the control unit 100. In addition, the spindle current value increases when the grinding load (referring to the load that hinders the rotation of the grinding wheels 32 and 42) of the grinding units 3 and 4 increases, and decreases when the grinding load decreases.

[0036] In addition, grinding units 3 and 4 have Figure 3The grinding water supply unit 14 is shown. The grinding water supply unit 14 supplies grinding water to the upper surface of the workpiece held by the worktable 7, i.e., the back surface 205 of the workpiece 200, in a manner that allows for adjustable flow rate. For example... Figure 3 As shown, the grinding water supply unit 14 includes a grinding water supply source 141, a grinding water supply flow path 142, and a grinding water supply nozzle 143. The grinding water supply source 141 supplies grinding water to the grinding water supply flow path 142 and the grinding water supply nozzle 143.

[0037] The grinding water supply path 142 includes: an inner spindle flow path 144 extending axially at the center of the spindle 33; an inner mounting path 145 communicating with the inner spindle flow path 144 and extending from the inner spindle flow path 144 toward the outer periphery of the grinding wheel mounting 37, and opening on the lower surface of the grinding wheel mounting 37; and an inner base flow path 146 communicating with the inner mounting path 145 and opening on the inner circumferential surface of the annular base 35 of the grinding wheels 32 and 42. The inner spindle flow path 144 is a flow path disposed within the spindle 33, the inner mounting path 145 is a flow path disposed within the grinding wheel mounting 37, and the inner base flow path 146 is a flow path disposed within the annular base 35. The grinding water supply path 142 provides grinding water from the grinding water supply source 141 through the flow paths 144, 145, and 146 to the inner circumferential surface of the annular base 35 of the grinding wheels 32 and 42, thereby providing grinding water to the grinding tools 31 and 41 that grind the workpiece 200 and the workpiece 200.

[0038] The grinding water supply nozzle 143 is disposed below the lower surface of the grinding wheels 32 and 42 of the grinding units 3 and 4, and inside the plurality of grinding tools 31 and 41 of the grinding wheels 32 and 42 in the grinding units 3 and 4 during grinding. The grinding water supply nozzle 143 is disposed below the lower surface of the grinding wheels 32 and 42 of the grinding units 3 and 4, and extends from the center of the grinding wheels 32 and 42 in the grinding units 3 and 4 during grinding towards the center of the holding surface 71 of the holding table 7 located in the processing position (i.e., the grinding tools 31 and 41 located in the processing position), and supplies grinding water from the grinding water supply source 141 to the grinding tools 31 and 41 located in the processing position. In addition, the grinding tools 31 and 41 located in the processing position refer to the grinding tools 31 and 41 located at the center of the holding surface 71 of the holding table 7 among the plurality of grinding tools 31 and 41 rotating about the axis.

[0039] Additionally, in this embodiment, the grinding water supply unit 14 includes: a flow regulating valve 147 that controls the flow rate (equivalent to the grinding water volume) of the grinding water supplied to the grinding water supply flow path 142; and a flow regulating valve 148 that controls the flow rate of the grinding water supplied to the grinding water supply nozzle 143.

[0040] The grinding feed unit 5 moves the grinding units 3 and 4 in the Z-axis direction, causing them to move away from and closer to the holding table 7. In this embodiment, the grinding feed unit 5 is mounted on a vertical column 21 erected at one end in the Y-axis direction, which is parallel to the horizontal direction of the device body 2. The grinding feed unit 5 includes: a known ball screw rotatable about an axis; a known electric motor that rotates the ball screw about an axis; and a known guide rail that supports the spindle housing 36 of each grinding unit 3 and 4 so that it can move freely in the Z-axis direction.

[0041] In addition, in the embodiment, for the rough grinding unit 3 and the fine grinding unit 4, the rotation centers (or axes) of the grinding wheels 32 and 42 and the rotation centers (or axes) of the holding table 7 are arranged parallel to each other in the horizontal direction, and the grinding tools 31 and 41 pass over the center of the back surface 205 of the workpiece 200 held by the holding table 7.

[0042] Boxes 8 and 9 are storage containers with multiple slots for storing the workpiece 200. Boxes 8 and 9 store the workpiece 200 before and after grinding. In addition, the alignment unit 10 is a worktable for temporarily placing the workpiece 200 taken out from boxes 8 and 9 and for centering the workpiece 200.

[0043] Two conveying units 11 are provided. Each conveying unit 11 has an adsorption pad for adsorbing the workpiece 200. One conveying unit 11 adsorbs and holds the workpiece 200 before grinding, which has been aligned using the alignment unit 10, and moves it onto the holding table 7 located in the conveying-in / conveying area 301. The other conveying unit 11 adsorbs and holds the workpiece 200 after grinding, which is held on the holding table 7 in the conveying-in / conveying area 301, and moves it to the cleaning unit 12.

[0044] The cleaning unit 12 cleans the workpiece 200 after grinding, removing grinding chips and other contaminants adhering to the back surface 205. The loading / unloading unit 13 is, for example, a robotic picker with a U-shaped arm 131, which uses the U-shaped arm 131 to hold and transport the workpiece 200. Specifically, the loading / unloading unit 13 removes the workpiece 200 from the boxes 8 and 9 before grinding and moves it to the alignment unit 10, and removes the workpiece 200 after grinding from the cleaning unit 12 and moves it into the boxes 8 and 9.

[0045] Additionally, the grinding apparatus 1 includes a thickness measuring device (not shown) that measures the thickness of the workpiece 200 held by the holding table 7 in the rough grinding zone 302 and the fine grinding zone 303. The thickness measuring device outputs the measurement result to the control unit 100.

[0046] The control unit 100 controls each of the aforementioned structural units constituting the grinding apparatus 1. That is, the control unit 100 causes the grinding apparatus 1 to perform grinding operations on the workpiece 200. The control unit 100 is a computer, and it includes: an arithmetic processing unit having a microprocessor such as a CPU (central processing unit); a storage device having a memory such as ROM (read-only memory) or RAM (random access memory); and an input / output interface device.

[0047] The arithmetic processing unit of the control unit 100 performs arithmetic processing according to a computer program stored in a storage device, and outputs control signals for controlling the grinding apparatus 1 to the aforementioned components of the grinding apparatus 1 via an input / output interface device. Furthermore, the control unit 100 is connected to a display unit, such as a liquid crystal display device that displays the status or image of the machining operation, and an input unit used by the operator to register machining information. The input unit consists of at least one of a touch panel and a keyboard provided on the display unit.

[0048] The grinding apparatus 1 with the above-described structure controls each structural unit through the control unit 100, thereby sequentially performing rough grinding and fine grinding on the workpiece 200 to thin it. In this embodiment, the operator places the workpiece 200, with the protective component 210 facing downwards, into the main body 2 of the grinding apparatus 1, registers the processing conditions in the control unit 100, and begins the processing operation when the control unit 100 receives a start instruction from the operator.

[0049] During the machining process, the grinding unit 1 rotates the spindles 33 of each grinding unit 3 and 4 around their axis at a speed set in the machining conditions. A workpiece 200 is retrieved from the box 8 via the loading / unloading unit 13 and transported to the alignment unit 10. The grinding unit 1 then aligns the workpiece 200 at its center via the alignment unit 10. The conveying unit 11 then moves the aligned workpiece 200, with its front side 202, onto the holding table 7 located in the loading / unloading area 301. At this time, the workpiece 200, moved onto the holding table 7, is positioned coaxially with the holding table 7.

[0050] During the machining operation, the grinding device 1 attracts and holds the workpiece 200 in the loading / unloading area 301 via the protective member 210, with the front 202 side of the workpiece 200 in the holding table 7. The rotary table 6 rotates, moving the holding table 7, which holds the workpiece 200 in the loading / unloading area 301, to the rough grinding area 302. During the machining operation, the grinding device 1 performs rough grinding on the workpiece 200 while supplying grinding water and rotating the holding table 7 around its axis via the rough grinding unit 3. The rotary table 6 rotates, moving the holding table 7, which holds the workpiece 200 after rough grinding, to the finish grinding area 303. The grinding device 1 performs fine grinding on the workpiece 200 while supplying grinding water and rotating the holding table 7 around the axis through the fine grinding unit 4. The rotating table 6 moves the holding table 7, which holds the workpiece 200 after fine grinding and stops rotating around the axis, to the loading and unloading area 301.

[0051] During the machining process, the grinding device 1 transfers the workpiece 200, after fine grinding, from the holding table 7 in the transfer area 301 to the cleaning unit 12. After cleaning by the cleaning unit 12, it is stored in the boxes 8 and 9. During the machining process, whenever the turntable 6 rotates, the grinding device 1 transfers the workpiece 200 into the holding table 7 in the transfer area 301 (where the workpiece 200 after fine grinding is not held). After transferring the workpiece 200 from the holding table 7 in the transfer area 301 to the cleaning unit 12, it transfers the workpiece 200 before grinding. The grinding device 1 ends the machining process when it has performed rough grinding and fine grinding on all the workpieces 200 in the boxes 8 and 9. Next, the grinding method for the workpieces will be described.

[0052] (Grinding method for the workpiece)

[0053] The grinding method of the workpiece in the embodiment uses the above-described grinding apparatus 1 to thin the workpiece 200 to a predetermined finished thickness 206. Figure 2 The grinding method shown is implemented in the rough grinding unit 3 in this embodiment. Therefore, in this embodiment, the specified finished thickness 206 refers to the thickness of the workpiece 200 after rough grinding by the rough grinding unit 3, and may not be consistent with the thickness of the workpiece 200 after fine grinding.

[0054] like Figure 4 As shown, the grinding method for the workpiece in the embodiment includes a first grinding step 1001 and a second grinding step 1002. That is, in the embodiment, the first grinding step 1001 and the second grinding step 1002 are performed in the rough grinding unit 3.

[0055] (Grinding Step 1)

[0056] The first grinding step 1001 is as follows: while applying a first grinding water flow rate 401 (which is capable of suppressing the consumption of the grinding wheel 31), Figure 5 The grinding water (shown) is supplied to the grinding wheel 31, and the workpiece 200 is ground to a predetermined thickness by the rough grinding unit 3. In addition, the predetermined thickness is a thickness that is thicker than the finished thickness 206, and is appropriately set according to the type of workpiece 200, the type of grinding wheel 31 of the rough grinding unit 3, etc.

[0057] The grinding apparatus 1 supplies grinding water of a first grinding water volume 401 from the grinding water supply unit 14 to the grinding wheel 32 of the rough grinding unit 3 and the grinding tool 31, while the grinding feed unit 5 brings the rough grinding unit 3 close to the workpiece 200 held by the holding table 7 of the rough grinding area 302, so that the grinding tool 31 of the rough grinding unit 3 comes into contact with the workpiece 200 and the rough grinding process and the first grinding step 1001 begin, gradually thinning the workpiece 200. Furthermore, the first grinding water volume 401 of the first grinding step 1001 is the sum of the flow rate of the grinding water supplied to the grinding water supply flow path 142 and the flow rate of the grinding water supplied to the grinding water supply nozzle 143. In addition, the first grinding water volume 401 is equal to the water volume (flow rate) when the conventional coarse grinding unit 3 performs coarse grinding on the workpiece 200, that is, when the conventional grinding device performs grinding on the workpiece 200.

[0058] Thus, in the first grinding step 1001, grinding water of the same first grinding water volume 401 as in the past is supplied from the grinding water supply unit 14 to the grinding wheel 32 of the rough grinding unit 3 to the grinding tool 31, thereby suppressing the consumption of the grinding tool 31 of the rough grinding unit 3. The first grinding water volume 401 that suppresses the consumption of the grinding tool 31 refers to the same water volume (flow rate) as when the rough grinding unit 3 performs rough grinding on the workpiece 200, i.e., when the grinding device used in the past grinds the workpiece 200.

[0059] in addition, Figure 5 The horizontal axis represents time, the right vertical axis represents the amount of grinding water supplied to the rough grinding unit 3, and the left vertical axis represents the spindle current value of the rough grinding unit 3. Additionally, Figure 5 The dashed line in the figure shows the change in the amount of grinding water supplied to the rough grinding unit 3. Figure 5 The solid line in the figure shows the change in the spindle current value of the rough grinding unit 3.

[0060] In one embodiment, in the first grinding step 1001, the grinding feed unit 5 reduces the grinding feed rate of the rough grinding unit 3, which is close to the holding table 7, in stages according to the thickness of the workpiece 200. In another embodiment, in the first grinding step 1001, the grinding feed unit 5 reduces the grinding feed rate of the rough grinding unit 3 in three stages; however, in this invention, the stages for reducing the grinding feed rate are not limited to three stages.

[0061] In the first grinding step 1001, as Figure 5 As shown, in the grinding apparatus 1, because the consumption of the bonding agent in the grinding wheel 31 of the rough grinding unit 3 is suppressed, spontaneous sharpening cannot be promoted. Due to the influence of grinding chips, etc., the surface gradually becomes smooth, and the spindle current value of the rough grinding unit 3 slowly increases. In the first grinding step 1001, as... Figure 5 As shown, the grinding device 1 maintains the grinding water volume at the first grinding water volume 401 to thin the workpiece 200 to the specified thickness.

[0062] (Second grinding step)

[0063] The second grinding step 1002 is as follows: After performing the first grinding step 1001, while providing grinding water of the second grinding water volume 402, which reduces the grinding water volume compared to the first grinding water volume 401 and increases the consumption of the grinding tool 31 to promote spontaneous sharpening, the rough grinding unit 3 is fed to grind the workpiece 200 to a finished thickness 206, promotes the sharpening of the grinding tool 31, and prepares for rough grinding of the next workpiece 200.

[0064] In the second grinding step 1002, the grinding apparatus 1 lowers the grinding feed rate of the rough grinding unit 3 based on the grinding feed unit 5 than the grinding feed rate of the first grinding step 1001, such as... Figure 5 As shown, the flow regulating valves 147 and 148 are controlled to reduce the amount of grinding water supplied by the grinding water supply unit 14 to the grinding wheel 32 of the rough grinding unit 3 to a second grinding water volume 402, which is lower than the first grinding water volume 401. As a result, the bonding agent of the grinding wheel 31 in the rough grinding unit 3 wears away, promoting spontaneous sharpening by detaching the abrasive grains from the bonding agent. In the second grinding step 1002, the grinding wheel 31 of the rough grinding unit 3, which was flattened due to grinding chips and the like in the first grinding step 1001, is sharpened as follows: spontaneous sharpening is promoted, thereby enabling rough grinding processing using new abrasive grains.

[0065] Therefore, in the second grinding step 1002, the grinding device 1 promotes the spontaneous sharpening of the grinding wheel 31 of the rough grinding unit 3, thus achieving sharpening. Figure 5As shown, compared to the first grinding step 1001, the grinding load is reduced and the spindle current value is reduced. In the second grinding step 1002, when the workpiece 200 is thinned to the finished thickness 206, the grinding device 1 stops the grinding feed of the rough grinding unit 3 based on the grinding feed unit 5, and then the rough grinding unit 3 is moved away from the holding table 7 by the grinding feed unit 5, thus ending the second grinding step 1002 and the rough grinding of the workpiece 200.

[0066] Furthermore, in the rough grinding unit 3, the grinding apparatus 1 sequentially performs the first grinding step 1001 and the second grinding step 1002 on the next workpiece 200 (hereinafter referred to as the (n+1)th workpiece, which is positioned in the rough grinding area 302 by the rotation of the turntable 6) held by the holding table 7. At this time, when the second grinding step 1002 is performed on the previous workpiece 200 (hereinafter referred to as the nth workpiece), the grinding tool 31 of the rough grinding unit 3 is sharpened. Therefore, when the first grinding step 1001 is performed on the (n+1)th workpiece 200, from the moment the first grinding step 1001 begins, the grinding tool 31 grips the workpiece 200, and the grinding load does not increase sharply. Figure 5 As shown, the spindle current value did not rise sharply all at once, but rose slowly, similar to when grinding the nth workpiece 200. Furthermore, Figure 5 This shows the case where n=1.

[0067] As described above, the workpiece grinding method of the embodiment makes the grinding water volume in the second grinding step 1002 of the latter half of the grinding process of the workpiece 200 a second grinding water volume 402 that is lower than the first grinding water volume 401 in the first grinding step 1001, thereby promoting the spontaneous sharpening of the grinding wheel 31. Therefore, the workpiece grinding method of the embodiment can start the rough grinding process of the next workpiece 200 in a sufficiently sharpened state. When the rough grinding process of the (n+1)th workpiece 200 begins, the grinding wheel 31 easily grips the workpiece 200, which can suppress the grinding load at the beginning of the rough grinding process of the (n+1)th workpiece 200, thereby preventing the increase of the spindle current value at the beginning of the rough grinding process of the (n+1)th workpiece 200.

[0068] Furthermore, the grinding method of the workpiece in this embodiment uses a first grinding water quantity 401 in the first half of the grinding process on the workpiece 200, which is equal to and higher than the second grinding water quantity 402. This suppresses the consumption of the grinding tool 31 in the first grinding step 1001. In the latter half of the grinding process, the grinding water quantity is reduced to the second grinding water quantity 402, increasing consumption and promoting spontaneous sharpening. Therefore, the grinding method of the workpiece in this embodiment can prevent excessive consumption of the grinding tool 31 and reduce the grinding load.

[0069] Furthermore, the workpiece grinding method of the embodiment uses a grinding apparatus 1 that performs rough grinding and fine grinding. Therefore, in the second grinding step 1002 of the rough grinding unit 3, the amount of grinding water is reduced to promote spontaneous sharpening. The workpiece grinding method of the embodiment uses a grinding wheel 31 that promotes spontaneous sharpening in the second grinding step 1002. Compared with the case where the amount of grinding water is kept constant from the beginning to the end of grinding, or compared with the conventional method of grinding by increasing the amount of grinding water in the second half of grinding compared with the first half, it is possible to intentionally roughen the grinding surface, i.e., the back surface 205, of the workpiece 200 after rough grinding based on the rough grinding unit 3 (equivalent to increasing the surface roughness by inflicting damage). Therefore, the grinding method for the workpiece in the embodiment uses a grinding apparatus 1 that performs rough grinding and fine grinding. Thus, when grinding with a fine grinding wheel 42 for fine grinding with a finer abrasive grain size during fine grinding, the grinding tool 41 of the fine grinding wheel 42 is easily gripped due to the unevenness of the back surface 205 of the workpiece 200, and wear is also promoted. Even with a fine grinding wheel 42 for fine grinding that is more difficult to grip, grinding can be achieved with reduced grinding load.

[0070] As a result, the grinding method for the workpiece in the embodiment has the following effects: it can prevent excessive wear of the grinding tool 31 and also reduce the grinding load.

[0071] Furthermore, the grinding method for the workpiece in the embodiment uses a grinding apparatus 1 that performs rough grinding and fine grinding. Therefore, even if the back surface 205 of the workpiece 200 is roughened by the rough grinding unit 3, the surface roughness of the back surface 205 of the workpiece 200 can be reduced by fine grinding. Thus, the grinding load can be reduced, and the processing quality of the workpiece 200 can be maintained at a high level.

[0072] Next, the applicants of this invention confirmed the effectiveness of the grinding method for the workpiece according to the embodiments. In the confirmation, in... Figure 6 Comparative Example 1 and Figure 7In Comparative Example 2 shown, the spindle current values ​​were measured when rough grinding of the nth workpiece 200 and the (n+1)th workpiece 200 was performed using the rough grinding unit 3. Furthermore, in the verification, n = 1. Figure 6 This is a graph showing the changes in the amount of grinding water and the spindle current value in Comparative Example 1. Figure 7 This is a graph showing the changes in the amount of grinding water and the spindle current value in Comparative Example 2.

[0073] In addition, with Figure 5 same, Figure 6 and Figure 7 In the diagram, the horizontal axis represents time, the right vertical axis represents the amount of grinding water supplied to the rough grinding unit 3, and the left vertical axis represents the spindle current value of the rough grinding unit 3. Additionally, Figure 6 and Figure 7 In the diagram, the dashed line shows the change in the amount of grinding water supplied to the rough grinding unit 3, and the solid line shows the change in the spindle current value of the rough grinding unit 3.

[0074] Regarding Figure 6 Comparative Example 1, showing the spindle current value, describes maintaining the grinding water volume at the first grinding water volume 401 during rough grinding based on the rough grinding unit 3, while keeping other conditions the same as in the implementation method (i.e., not increasing or decreasing the grinding water volume from the first grinding water volume 401 from the very beginning of the rough grinding process until the end of the process). Regarding... Figure 7 Comparative Example 2, which shows the spindle current value, sets the grinding water volume after the (n+1)th workpiece 200 has just started rough grinding to the second grinding water volume 402, and then maintains it at the first grinding water volume 401, with other conditions being the same as in the implementation method (equivalent to the method shown in Patent Document 3 above) (that is, the grinding water volume after the start of rough grinding is less than that in the second half of rough grinding, and the grinding water volume in the second half of rough grinding is more than that in the first half of grinding).

[0075] according to Figure 6 In Comparative Example 1, the first grinding water flow rate 401, which suppresses wear on the grinding wheel 31, is maintained, thus causing blockage of the grinding wheel 31. At the start of the rough grinding of the (n+1)th workpiece 200, the spindle current value suddenly increases. Furthermore, according to... Figure 7 In Comparative Example 2, the second grinding water volume 402, which is less than the first grinding water volume 401 used in the first half of the rough grinding process, is changed in the latter half of the rough grinding process to suppress the consumption of the grinding wheel 31. Therefore, when the grinding begins with the grinding wheel 31 being ground flat, at which the maximum grinding load is applied to the next workpiece 200, the grinding load increases further. At the start of the rough grinding process of the (n+1)th workpiece 200, the spindle current value increases suddenly. Therefore, according to Figure 6 and Figure 7It can be seen that in Comparative Example 1 and Comparative Example 2, the grinding load suddenly increases at the start of the rough grinding process of the (n+1)th workpiece 200. The sudden and sharp increase in grinding load can easily cause scratches or damage to the grinding wheel 31 and the workpiece 200, and is therefore not preferred.

[0076] Compared to Comparative Example 1 and Comparative Example 2, in the implementation, as... Figure 5 As shown, at the start of the rough grinding of the (n+1)th workpiece 200, the spindle current value does not rise suddenly, and the grinding load does not rise suddenly. Therefore, it can be seen that by making the grinding water volume of the second grinding step 1002 in the latter half of the grinding process of the workpiece 200 a second grinding water volume 402 that is lower than the first grinding water volume 401 in the first grinding step 1001, the spontaneous sharpening of the grinding wheel 31 can be promoted, and the grinding load at the start of the rough grinding of the (n+1)th workpiece 200 can be suppressed.

[0077] Furthermore, the present invention is not limited to the embodiments described above. That is, various modifications and implementations can be made without departing from the spirit of the present invention. In addition, in the embodiments, the grinding water supply unit 14 includes: a flow regulating valve 147 that controls the flow rate (equivalent to the grinding water volume) of the grinding water supplied to the grinding water supply flow path 142; and a flow regulating valve 148 that controls the flow rate of the grinding water supplied to the grinding water supply nozzle 143. However, the grinding water supply unit 14 may have at least one of the following: the grinding water supply flow path 142 and the flow regulating valve 147, or the grinding water supply nozzle 143 and the flow regulating valve 148. Furthermore, when changing the grinding water volume from the first grinding water volume 401 to the second grinding water volume 402, in the embodiments, both the flow regulating valve 147 and the flow regulating valve 148 are adjusted, but only one of them may be adjusted.

Claims

1. A grinding method for a workpiece, comprising using a grinding apparatus to thin the workpiece to a finished thickness. This grinding device has the following features: Maintain the worktable, which holds the workpiece in place; A grinding unit having a spindle for mounting a grinding wheel and an electric motor for driving the spindle to rotate, wherein a grinding tool for grinding the workpiece held by the holding table is arranged in a ring on the grinding wheel. The grinding feed unit moves the grinding unit away from and towards the holding table relative to it; A grinding water supply unit that supplies grinding water to the upper surface of the workpiece held by the holding table in a manner that allows for adjustable flow rate; as well as A control unit that controls each of the aforementioned units. The grinding method for the workpiece includes the following steps: In the first grinding step, while providing grinding water at a first constant grinding water volume capable of suppressing the consumption of the grinding wheel, the grinding unit feeds the workpiece at a first grinding feed rate to grind it to a predetermined thickness; and In the second grinding step, when the specified thickness of the workpiece achieved in the first grinding step is reached, the grinding feed of the grinding unit is changed to a second grinding feed speed lower than the first grinding feed speed, and the supply of grinding water is changed to a second constant grinding water volume reduced relative to the first constant grinding water volume. While providing the grinding water at the second constant grinding water volume, the workpiece is ground to the finished thickness, wherein the consumption of the grinding tool is increased in the second grinding step to promote the spontaneous sharpening of the grinding tool.

2. The grinding method for a workpiece according to claim 1, wherein, The grinding unit includes: The rough grinding unit uses coarse-grit grinding wheels; and The fine grinding unit uses fine-grit grinding wheels to grind the workpiece that has been ground by the coarse grinding unit. The first grinding step and the second grinding step are performed in the coarse grinding unit.

3. The grinding method for a workpiece according to claim 1, wherein, The grinding water is supplied to the upper surface of the workpiece through the spindle internal flow path, the mounting base internal flow path, and the base internal flow path. The spindle internal flow path extends along the axis of the spindle. The mounting base internal flow path communicates with the spindle internal flow path and extends from the spindle internal flow path toward the outer periphery of the grinding wheel mounting base on which the grinding wheel is mounted, and opens on the lower surface of the grinding wheel mounting base. The base internal flow path communicates with the mounting base internal flow path and opens on the inner circumferential surface of the annular base of the grinding wheel.

4. The grinding method for a workpiece according to claim 3, wherein, The grinding water is also supplied to the upper surface of the workpiece through a grinding water supply nozzle disposed below the lower surface of the grinding wheel and inside the grinding tool arranged in a ring on the grinding wheel.

5. The grinding method for a workpiece according to claim 4, wherein, The first constant grinding water volume is the sum of the flow rate of grinding water supplied to the spindle internal flow path, the mounting internal flow path, and the base internal flow path and the flow rate of grinding water supplied to the grinding water supply nozzle.

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