METHOD FOR MACHINING A WORKPIECE

Abstract

Method for machining a workpiece (11) comprising: a holding step (S10) for holding an end face (11a) of the workpiece (11) on a holding table (10) which has an area made of a transparent material, while a rear face (11b) of the workpiece (11) is exposed; and a machining groove training step (S30, S35) involving the training of a machining groove (13a) in the workpiece (11) by cutting the workpiece (11) held on the holding table (10) with a cutting blade (84a, 84b), where the processing groove training step (S30) exhibits: a first image acquisition step (S31) by taking an image of the machining groove (13a) on the back (11b) of the workpiece (11), a second image acquisition step (S36) with an image of the machining groove (13a) on the end face (11a) of the workpiece (10) being taken through the holding table (10), and a capture step (S32, S37) with a capture of whether a position of a first center line (13a2) of the processing groove (13a), whose image was captured in the first image acquisition step (S31), and a position of a second center line (13b2) of the processing groove (13a), whose image was captured in the second image acquisition step (S36), coincide in a predetermined plane or not, and If the position of the first center line (13a2) and the position of the second center line (13b2) do not match in the predetermined plane during the capture step (S32, S37), then the machining groove training step (S30) further includes a correction step (S33, S38) with a correction of a position of a center of the cutting blade (84a) to bring the position of the first center line (13a2) and the position of the second center line (13b2) into agreement.

Description

BACKGROUND OF THE INVENTION AREA OF THE INVENTION

[0001] The present invention relates to a method for machining a workpiece whose end face is held on a holding table which has an area made of a material that is transparent to visible light. DESCRIPTION OF THE RELATED STATE OF THE ART

[0002] Electronic component chips are used in electronic devices such as mobile phones and personal computers. These chips are manufactured by dividing workpieces, such as silicon wafers, which have multiple components, such as integrated circuits (ICs), large-area integrated circuits (LSI), microelectromechanical systems (MEMS), or similar devices, embedded on their end faces. Specifically, the back side of such a workpiece is ground down by a grinding device until it is thinned to a predetermined thickness. The workpiece is then divided into individual component chips by a cutting device, which includes a cutting unit and a clamping table, along projected parting lines.

[0003] Since components have become more diverse in recent years, a cutting method is known for cutting a workpiece along projected parting lines, while one end face of the workpiece, where components are formed, is facing downwards and held under suction on a clamping table (see, for example, JP 2006-140 341 A). Normally, alignment marks are formed on the end face of such a workpiece, which are used to determine the positions of the projected parting lines. In a case where the end face of the workpiece is exposed with its back side facing upwards and held under suction on the clamping table, it is necessary to position a camera unit capable of capturing workpiece images with infrared beams and capturing an image of the end face of the workpiece through its back side with the camera unit positioned above the workpiece.

[0004] A cutting device is known that comprises a clamping table transparent to visible light and a camera unit arranged below the clamping table for capturing workpiece images with visible light (see, for example, JP 2010-87141A). Even when the end face of a workpiece is held against the clamping table under suction, the cutting device allows the camera unit to capture an image of the workpiece end face with visible light through the clamping table. Therefore, the cutting device can align the workpiece against the clamping table with a cutting unit based on the image captured by the camera unit, without the need for an infrared camera unit.

[0005] In a case where the workpiece to be cut is made of a hard material or is relatively thick, a cutting method known as stepwise cutting was used. This method cuts the workpiece by repeatedly cutting along each of the projected parting lines formed on the workpiece's face. As with the standard stepwise cutting method, the back of the workpiece is held under suction on a clamping table made of a porous ceramic or similar material, so that the workpiece's face is exposed upwards.The workpiece is then aligned with a cutting unit using a camera unit based on an image taken from the front face of the workpiece by a visible light camera positioned above the workpiece, and the projected parting lines on the workpiece are essentially aligned parallel to the direction in which the workpiece and the cutting unit are to be fed relative to each other for processing.

[0006] A first cutting blade then cuts the workpiece along the projected parting lines, creating initial machining grooves along these lines to a predetermined depth less than the workpiece thickness, meaning the workpiece is not fully divided. A second cutting blade, thinner than the first, then cuts the bottoms of these initial machining grooves, creating secondary machining grooves that are narrower than the initial ones, along the projected parting line to a depth sufficient to reach the back of the workpiece. Thus, in accordance with the step-cutting process, the workpiece is divided by the initial machining grooves, located closer to its end face, and the secondary machining grooves, located closer to its back face.However, if the camera unit captures an image of the machining grooves in the workpiece from above, the image does not include the second machining grooves, which are positioned closer to the back of the workpiece. Consequently, it is not possible to confirm from the captured image whether the center lines of the first machining grooves and the center lines of the second machining grooves are the same width.

[0007] German patent application JP 2010-087 141 A discloses a processing device for laser cutting of semiconductor wafers and, in particular, an alignment imaging section of the processing device. The latter aims to position a workpiece, which has a layer that does not transmit light between the processing device and the object to be imaged, on the clamping table with its surface facing downwards and to perform an alignment without being affected by the structure of the workpiece. Further cutting devices and methods are proposed in German patent applications JP 2018-206 995 A and JP 2009-289 786 A. SUMMARY OF THE INVENTION

[0008] It is therefore an object of the present invention to provide a method for machining a workpiece in order to cut the workpiece with machining grooves along projected parting lines on the workpiece in such a way that the center lines of the first machining grooves cut into the workpiece coincide with the center lines of the second machining grooves cut into the workpiece.

[0009] In accordance with one aspect of the present invention, a method for machining a workpiece is provided, wherein the method comprises a holding step comprising holding an end face of the workpiece on a holding table having a region made of a transparent material while a rear face of the workpiece is exposed, and a machining groove formation step comprising forming a machining groove in the workpiece by cutting the workpiece held on the holding table with a cutting blade, wherein the machining groove formation step comprises a first image acquisition step comprising acquiring an image of the machining groove on the rear face of the workpiece, a second image acquisition step comprising acquiring an image of the machining groove on the end face of the workpiece through the holding table, and a detection step comprising detecting whether a position of a first center line of the machining groove,whose image was captured during the first image acquisition step, and a position of a second center line of the processing groove, whose image was captured during the second image acquisition step, coincides in a predetermined plane, and if the position of the first center line and the position of the second center line do not coincide in the predetermined plane during the acquisition step, the processing groove training step further includes a correction step with a correction of a position of a center of the cutting blade to bring the position of the first center line and the position of the second center line into agreement.

[0010] The machining groove formation step can consist of a first machining groove formation step with the formation of a first machining groove in the workpiece, wherein the first machining groove has a predetermined depth to just before the end face, with a first cutting blade having a first thickness, and a second machining groove formation step with the positioning of a second cutting blade having a second thickness, at the first machining groove and the formation of a second machining groove in the workpiece along the first machining groove, wherein the second machining groove extends to the end face, thereby dividing the workpiece.

[0011] The second cutting blade can have a smaller edge thickness than the first cutting blade.

[0012] The first image acquisition step can include capturing an image of the first machining groove on the back side with visible light using a first image acquisition unit positioned above the workpiece, the second image acquisition step can include capturing an image of the second machining groove on the front side with visible light through the holding table using a second image acquisition unit positioned below the workpiece, and the detection step can include detecting whether a position of a first center line of the first machining groove on the back side and a position of a second center line of the second machining groove on the front side coincide in the predetermined plane.

[0013] The first image acquisition step can include capturing an image of the first machining groove on the back side using infrared radiation through the holding table and a third image acquisition unit located under the workpiece; the second image acquisition step can include capturing an image of the second machining groove on the front side using infrared radiation through the holding table and the third image acquisition unit; and the detection step can include determining whether the position of the first center line of the first machining groove on the back side and the position of the second center line of the second machining groove on the front side coincide in the predetermined plane.

[0014] In the method for machining the workpiece in accordance with the present invention, an image of the machining groove on the back side of the workpiece is taken (first image acquisition step), and an image of the machining groove on the front side of the workpiece is taken (second image acquisition step). Then, it is determined whether the position of the first center line of the machining groove, the image of which was taken in the first image acquisition step, and the position of the second center line of the machining groove, the image of which was taken in the second image acquisition step, coincide in the predetermined plane (acquisition step).

[0015] If the position of the first center line and the position of the second center line do not coincide in the predetermined plane, the position of the cutting blade's center is corrected to align the positions of the first and second center lines (correction step). In a subsequent cutting operation, the center in the width direction of the machining groove on the back of the workpiece and the center in the width direction of the machining groove on the front of the workpiece are thus kept aligned.

[0016] The above and other problems, features and advantages of the present invention, as well as the manner of its implementation, will best become clearer by studying the following description and attached claims, with reference to the attached drawings, which show some preferred embodiments of the invention, and the invention itself will be best understood thereby. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view of a cutting device performing a method for machining a workpiece in accordance with an embodiment of the present invention; Fig. Figure 2 is a perspective view of a workpiece unit that is to be handled by the cutting device; Fig. Figure 3 is a perspective view of a clamping table of the cutting device; Fig. Figure 4 is a partial sectional view of the clamping table from the side; Fig. Figure 5 is an enlarged sectional view of section A in Fig. 4; Fig. Figure 6 is an enlarged perspective view of a lower imaging unit of the cutting device; Fig. Figure 7 is a flowchart of the machining sequence of a cutting process in accordance with a first embodiment of the present invention as the method for machining a workpiece; Fig. Figure 8 is a sectional view illustrating a first machining groove formation step of the cutting process; Fig. Figure 9 is a sectional view illustrating the first image acquisition step of the cutting process; Fig. 10A is a view illustrating an example of an image that includes an initial editing groove; Fig. 10B is a view illustrating another example of an image that includes an initial editing groove; Fig. Figure 11 is a sectional view illustrating an additional first image acquisition step of the cutting process; Fig. Figure 12 is a sectional view illustrating a second image acquisition step of the cutting process; Fig. Figure 13 is a sectional view illustrating a second image acquisition step of the cutting process; Fig. 14A is a view illustrating an example of an image that includes a second editing groove; Fig. 14B is a view illustrating another example of an image that includes a second editing groove; Fig. Figure 15 is a sectional view of a workpiece after an additional second machining groove formation step of the cutting process has been carried out; Fig. Figure 16A is a sectional view illustrating a first image acquisition step of a cutting process in accordance with a second embodiment of the present invention; and Fig. Figure 16B is a sectional view illustrating a second image acquisition step of the cutting process in accordance with the second embodiment. DETAILED EXPLANATION OF THE PREFERRED EXECUTION FORMS

[0017] Preferred embodiments of the present invention are described below with reference to the accompanying drawings. Fig. Figure 1 illustrates, in perspective, a cutting device 2 in accordance with a first embodiment of the present invention. Fig. Figure 1 illustrates some components of the cutting device 2 in block form. Fig. Figure 1 illustrates the cutting device 2 in an XYZ coordinate system, which includes X-axis directions (i.e., feed directions), Y-axis directions (i.e., approach directions), and Z-axis directions (i.e., vertical directions), with the directions extending perpendicular to each other. The X-axis directions include a +X direction and a -X direction, which are opposite to each other; the Y-axis directions include a +Y direction and a -Y direction, which are opposite to each other; and the Z-axis directions include a +Z direction and a -Z direction, which are opposite to each other.

[0018] The cutting device 2 includes a base 4, which supports its components. The base 4 has an opening 4a, which is positioned in a front corner of it in a forward direction, i.e., the +Y direction. The opening 4a accommodates a cassette lift. The cassette lift has an upper surface on which a cassette 6 for receiving workpieces 11 is arranged (see Fig. 2) Each of the workpieces 11 includes a wafer, which is shaped, for example, as a circular plate, and made of a semiconductor material such as silicon. However, the workpiece 11 is not limited to a specific material, shape, structure, size, etc. The workpiece 11 can alternatively be made of any material, including other semiconductor materials, ceramics, resins, metals, etc.

[0019] As in Fig. As illustrated in Figure 2, the workpiece 11 has several intersecting projected dividing lines or paths 13 formed on its end face 11a. The projected dividing lines 13 delineate several areas on the end face 11a, each containing components 15, such as ICs, an alignment mark, etc. (not illustrated). A strip, i.e., a cutting strip, 17, whose diameter is larger than that of the workpiece 11, is attached to the end face 11a. The strip 17 has a layered structure comprising a base layer and an adhesive layer, i.e., a bonding layer, and is made of a transparent material through which radiation with a predetermined wavelength band, for example, visible light, infrared radiation, or the like, can be transmitted.

[0020] The base layer is made of, for example, polyolefin (PO) or a similar material. The adhesive layer is made of an adhesive resin, such as an ultraviolet (UV) curable adhesive resin. The adhesive layer of the strip 17 is attached to the end face 11a of the workpiece 11. An annular metal frame 19 is attached to an outer circumferential section of the strip 17, forming a workpiece unit 21 in which the workpiece 11 is supported by the strip 17 on the frame 19. Workpieces 11 are stored as workpiece units 21 in the cassette 6. Fig. Figure 2 illustrates the workpiece unit 21 in perspective.

[0021] As in Fig. As illustrated in Figure 1, the base 4 also has an elongated rectangular opening 4b, defined in the -Y direction behind the opening 4a, with longer sides extending along the X-axis directions. A clamping table, that is, a holding table, 10, shaped as a circular plate, is arranged in the opening 4b. An annular suction plate (not illustrated) with several suction openings defined therein along its circumferential directions is arranged on an outer circumferential section of the clamping table 10. The clamping table 10 and other related components are described with reference to the Fig. 3 to 6 are described in more detail.

[0022] Fig. Figure 3 illustrates the clamping table 10 in perspective. Fig. Figure 4 illustrates the clamping table 10 from the side and partially in section. Fig. For the sake of simplicity, hatching is omitted in section 4. Fig. 5 illustrates a section A in Fig. 4 in an enlarged sectional view. In Fig. Figure 5 illustrates a component in block form. The clamping table 10 has a holding element 12, which is shaped as a circular plate. The holding element 12 comprises a substantially flat surface 12a and another substantially flat surface 12b, which is positioned opposite surface 12a. The holding element 12 is made of a transparent material that transmits visible light and infrared radiation, such as near-infrared radiation. The holding element 12 is made of quartz glass, borosilicate glass, or soda glass, although it can also be made of calcium fluoride, lithium fluoride, or magnesium fluoride.

[0023] The retaining element 12 has several fluid channels defined within it. In particular, the fluid channels include a straight first suction channel 12c1, which, viewed in plan view, extends diametrically across the retaining element 12 along the Z-axis directions through the central axis of its circular plate, and a straight second suction channel 12c2, which extends diametrically across the retaining element 12 through the central axis of its circular plate perpendicular to the first suction channel 12c1 in a plane parallel to the surface 12a. The first suction channel 12c1 and the second suction channel 12c2 are connected to each other at a point 12c3, which is positioned at the central axis of the circular plate. The retaining element 12 also has several openings 12d, which are defined in an outer circumferential section of it at circumferentially spaced intervals.The openings 12d have upper ends that terminate at the surface 12a and extend from the surface 12a to a predetermined depth in the retaining element 12, where the openings 12d terminate just before the other surface 12b.

[0024] Some of the openings 12d are defined and connected at both ends of the first suction channel 12c1 and both ends of the second suction channel 12c2. The openings 12d are connected to each other circumferentially of the retaining element 12 by an outer circumferential suction channel 12e, which is defined in an outer circumferential section of the retaining element 12 at the predetermined depth. The openings 12d are also connected to a suction channel 12f (see Fig. 5), which is defined in the retaining element 12 and extends radially outwards. A suction source 14 (see Fig. 5), such as an ejector, is connected to the suction channel 12f. When the suction source 14 is actuated, it generates a negative pressure that acts through the suction channel 12f in the openings 12d. Therefore, the surface 12a of the holding element 12, where the openings 12d are open, serves as a holding surface for holding the workpiece unit 21, i.e., the workpiece 11, under suction.

[0025] The fluid channels in the retaining element 12, which include the first suction channel 12c1, the second suction channel 12c2, the openings 12d, the outer circumferential suction channel 12e, and the suction channel 12f, scatter or reflect light applied to the retaining element 12. Therefore, the fluid channels in the retaining element 12, when viewed from surface 12a or surface 12b, may not be completely transparent to visible light, but may be either translucent or opaque. However, areas of the retaining element 12, with the exception of these fluid channels, are transparent from surface 12a to surface 12b. In particular, four areas of the retaining element 12, separated by the first suction channel 12c1 and the second suction channel 12c2, and positioned radially inward relative to the outer circumferential suction channel 12e, are transparent from surface 12a to surface 12b.

[0026] A hollow cylindrical frame 16, made of a metallic material such as stainless steel, is arranged on an outer circumferential surface of the retaining element 12. The frame 16 has an opening 16a (see Fig. 5), which is defined in an upper section of this. The retaining element 12 is arranged in a covering relationship to the surface 12a on the frame 16. As in the Fig. 3 and Fig. As illustrated in Figure 4, the frame 16 is supported on an X-axis motion table 18. The X-axis motion table 18 includes a horizontal base plate 18a, which has a rectangular shape when viewed along the Z-axis directions. The X-axis motion table 18 also includes a vertical side plate 18b, which has a rectangular shape when viewed along the Y-axis directions and has a lower end that is connected in the +Y direction to a front end of the base plate 18a.

[0027] An upper plate 18c, which, like the base plate 18a, has a rectangular shape when viewed along the Z-axis directions, and which has a front end connected to an upper end of the side plate 18b. The base plate 18a, the vertical side plate 18b, and the upper plate 18c together define a space 18d between them, which is open in the -Y direction at its rear end and also at both side ends of the same in the X-axis direction. The base plate 18a is slidable on and along a pair of X-axis guide rails 20, which are arranged in the -Z direction beneath the base plate 18a and extend substantially parallel to each other in the X-axis directions. The X-axis guide rails 20 are fixedly attached to an upper face of a stationary base (not illustrated). A linear X-axis scale 20a is arranged adjacent to the X-axis guide rails 20.

[0028] A read head (not illustrated) is mounted on a lower surface of the X-axis motion table 18. The read head reads divisions of the linear X-axis scale 20a to calculate the position or coordinate in the X-axis directions of the X-axis motion table 18 and the distance the X-axis motion table 18 has moved in the X-axis directions. A nut (not illustrated) is mounted on a lower surface of the base plate 18a of the X-axis motion table 18 and is operatively connected to an X-axis ball screw 22 in threaded engagement. The ball screw is located between the X-axis guide rails 20 and extends substantially parallel to them. The X-axis ball screw 22 has one end coupled to an X-axis stepper motor 24.

[0029] When the X-axis stepper motor 24 is activated, it rotates the X-axis ball screw 22 about its central axis, causing the nut to move the X-axis motion table 18 in one of the X-axis directions along the X-axis guide rails 20. The X-axis motion table 18, the X-axis guide rails 20, the X-axis ball screw 22, the X-axis stepper motor 24, etc., together form an X-axis motion mechanism 26 for moving the X-axis motion table 18 along the X-axis guide rails 20. The frame 16 is rotatably supported on an upper surface of the upper plate 18c of the X-axis motion table 18 for rotation about a central axis that is essentially parallel to the Z-axis directions. The frame 16 includes a roller section 16b, which is defined by a cylindrical side surface of the frame.The roller section 16b of the frame 16, which is supported on the X-axis motion table 18, is positioned above the upper plate 18c of this.

[0030] A rotary actuator 30, such as an electric motor, is mounted on the side plate 18b of the X-axis motion table 18. The rotary actuator 30 has a shaft with a roller 30a attached to it. An endless belt 28 is wound around the roller 30a and the roller section 16b. When the rotary actuator 30 is activated, it rotates its shaft, which rotates the roller 30a to move the endless belt 28, thus rotating the frame 16 and consequently the clamping table 10 about its central axis, which is essentially parallel to the Z-axis directions. By controlling the rotation of the roller 30a, it is possible to rotate the clamping table 10 about its central axis through a desired angle.

[0031] A Y-axis motion mechanism 32 for moving a lower image acquisition unit 54, which will be described later, in the Y-axis directions is arranged in the X-axis directions as an extension of the X-axis motion mechanism 26. The Y-axis motion mechanism 32 includes a pair of Y-axis guide rails 34 that extend substantially parallel to each other in the Y-axis directions. The Y-axis guide rails 34 are fixedly mounted to the upper surface of the stationary base (not illustrated). A Y-axis motion table 36 is slidably mounted on and along the Y-axis guide rails 34. A nut (not illustrated) is attached to a lower surface of the Y-axis motion table 36 and is operatively engaged with a Y-axis ball screw 38, which is arranged between the Y-axis guide rails 34 and extends substantially parallel to them.

[0032] The Y-axis ball screw 38 has one end coupled to a Y-axis stepper motor 40. When the Y-axis stepper motor 40 is activated, it rotates the Y-axis ball screw 38 about its central axis, causing the nut to move the Y-axis motion table 36 along the Y-axis guide rails 34 in one of the Y-axis directions. The Y-axis guide rails 34, the Y-axis motion table 36, the Y-axis ball screw 38, the Y-axis stepper motor 40, etc., together form the Y-axis motion mechanism 32 for moving the Y-axis motion table 36 along the Y-axis guide rails 34. A non-illustrated linear Y-axis scale for use in detecting the position of the Y-axis motion table 36 in the Y-axis directions is arranged next to and extends along one of the Y-axis guide rails 34.A read head (not illustrated) is mounted on a lower surface of the Y-axis motion table 36 opposite the linear Y-axis scale. As the Y-axis motion table 36 moves along the Y-axis guide rails 34 in one of the Y-axis directions, the read head reads divisions of the linear Y-axis scale to calculate the position or coordinate of the Y-axis motion table 36 and the distance it has moved along the Y-axis directions.

[0033] A Z-axis motion mechanism 42 is arranged on an upper surface of the Y-axis motion table 36. Fig. Figure 6 illustrates the Z-axis motion mechanism 42 and other components in an enlarged perspective. The Z-axis motion mechanism 42 has a support structure 42a attached to the upper surface of the Y-axis motion table 36. A pair of Z-axis guide rails 44, extending substantially parallel to the Z-axis directions, is attached to a side surface of the support structure 42a facing the X-axis motion table. A Z-axis motion plate 46 is slidable on and along the Z-axis guide rails 44. A nut (not shown) is attached to a side surface of the Z-axis motion plate 46 facing the support structure 42a and engages in threaded engagement with a Z-axis ball screw 48, which is located between the Z-axis guide rails 44 and extends substantially parallel to them.

[0034] The Z-axis ball screw 48 has one end coupled to a Z-axis stepper motor 50. When the Z-axis stepper motor 50 is activated, it rotates the Z-axis ball screw 48 about its central axis, causing the nut to move the Z-axis motion plate 46 in one of the Z-axis directions along the Z-axis guide rails 44. The support structure 42a, the Z-axis guide rails 44, the Z-axis motion plate 46, the Z-axis ball screw 48, the Z-axis stepper motor 50, etc., together form the Z-axis motion mechanism 42 for moving the Z-axis motion plate 46 along the Z-axis guide rails 44. A non-illustrated linear Z-axis scale for use in detecting the position of the Z-axis motion plate 46 in the Z-axis directions is arranged next to and extends along one of the Z-axis guide rails 44.A read head (not illustrated) is mounted on a side face of the Z-axis motion plate 46 opposite the linear Z-axis scale. As the Z-axis motion plate 46 moves along the Z-axis guide rails 44 in one of the Z-axis directions, the read head reads divisions of the linear Z-axis scale to calculate the position or coordinate in the Z-axis directions of the Z-axis motion plate 46 and the distance the Z-axis motion plate 46 has moved in the Y-axis directions.

[0035] The lower image acquisition unit, that is, a second image acquisition unit, 54, is attached to the Z-axis motion plate 46 by a support arm 52, which is elongated in the X-axis directions. Fig. Figure 6 is an enlarged perspective view of the lower image acquisition unit 54. The lower image acquisition unit 54 includes a microscope camera unit comprising a low-magnification camera 56 and a high-magnification camera 58. Both the low-magnification camera 56 and the high-magnification camera 58 include an optical system with a condenser lens (not illustrated), etc., and an image acquisition device, such as a charge-coupled-device image sensor (CCD image sensor) or a complementary metal-oxide-semiconductor image sensor (CMOS image sensor), which are not illustrated.

[0036] In accordance with the present embodiment, the image acquisition device is capable of converting visible light photoelectrically into electrical signals. The lower image acquisition unit 54 is arranged in a position lower than the clamping table 10, and the optical axes of the condenser lenses are oriented substantially perpendicular to the other surface 12b of the holding element 12. An illumination device 56a for applying visible light to an object positioned above it, for example, the workpiece 11, is arranged along the low-magnification camera 56. Similarly, an illumination device 58a for applying visible light to an object positioned above it, i.e., the workpiece 11, is arranged along the high-resolution camera 58.To capture an image of the object with the low-resolution camera unit 54, the X-axis motion table 18 is moved in the direction of the Y-axis motion table 36 until the lower image acquisition unit 54 is positioned in space 18d at the X-axis motion table 18. The lower image acquisition unit 54 can then capture an image of the end face 11a of the workpiece 11, which is positioned on the surface 12a of the holding element 12, from below the holding element 12.

[0037] Other components of the cutting device 2 are described below with reference to Fig. 1. Bellows-shaped, dust- and splash-proof covers, which are flexibly expandable and retractable, are arranged in the opening 4b in a covering relationship on the left and right sides of the upper plate 18c of the X-axis motion table 18 in the +X direction and the -X direction, respectively. A portal-shaped support structure 4c is attached to an upper surface of the base 4 above and above the opening 4b. Two machining unit motion mechanisms, i.e., positioning units and cutting units 60, are arranged on a side surface of the support structure 4c that faces one side of the opening 4a of the base 4 in the -X direction. The machining unit motion mechanism 60 shares a pair of Y-axis guide rails 62, which are fixedly attached to the side surface of the support structure 4c.

[0038] The Y-axis guide rails 62 generally extend parallel to the Y-axis directions. The machining unit motion mechanisms 60 each include Y-axis motion plates 64, which are arranged to be independently displaceable on and along the Y-axis guide rails 62. Nuts (not illustrated) are attached to respective surfaces of the Y-axis motion plates 64 facing the support structure 4c and are engaged in threaded engagement with the Y-axis ball screws 66, which are arranged between and generally parallel to the Y-axis guide rails 62.In particular, the nut attached to one of the Y-axis motion plates 64, which is positioned at the front in the +Y direction, is in thread engagement with one of the Y-axis ball screws 66, whereas the nut attached to the other Y-axis motion plate 64, which is positioned at the rear in the -Y direction, is in thread engagement with the other Y-axis ball screw 66.

[0039] The Y-axis ball screws 66 each have ends that are coupled to Y-axis stepper motors 68 (one of which is illustrated). When the Y-axis stepper motors 68 are activated, they rotate the respective Y-axis ball screws 66 about their central axes, causing the respective nuts to move the Y-axis motion plates 64 along the Y-axis guide rails 62 in the Y-axis directions. The Y-axis motion plates 64 support pairs of Z-axis guide rails 72 on their surfaces facing away from the support structure 4c, extending substantially parallel to the Z-axis directions. A Z-axis motion plate 70a has a surface that is movable on and along the pair of Z-axis guide rails 72 on the other surface of the Y-axis motion plate 64, which is positioned at the rear in the -Y direction.Similarly, a Z-axis motion plate 70b has a surface that is displaceable on and along the pair of Z-axis guide rails 72 on the other surface of the Y-axis motion plate 64, which is positioned at the front in the +Y direction.

[0040] Nuts (not illustrated) are attached to respective surfaces of the Z-axis motion plates 70a and 70b, which face the support structure 4c, i.e., the Y-axis motion plates 64, and are operable via respective Z-axis ball screws 74 in threaded engagement. These ball screws are arranged between and generally parallel to the pairs of Z-axis guide rails 72. Each Z-axis ball screw 74 has ends coupled to respective Z-axis stepper motors 76. When the Z-axis stepper motors 76 are activated, they rotate the Z-axis ball screws 74 about their central axes, causing the nuts to move the Z-axis motion plates 70a and 70b along the Z-axis guide rails 72 in the Z-axis directions.

[0041] A first cutting unit 78a is attached to a lower section of the Z-axis motion plate 70a, which is positioned at the rear in the -Y direction. The first cutting unit 78a includes a tubular spindle housing 80a in which a section of a cylindrical spindle 82a (see Fig. 8) is rotatably mounted. The spindle 82a has one end that is coupled to a rotation mechanism (not illustrated), such as a servo motor, for rotating the spindle 82a about its central axis. A first cutting blade 84a with an annular cutting edge is attached to the other end of the spindle 82a. The first cutting blade 84a, in accordance with the present embodiment, is of the type of a washer, that is, of the hubless type, although it may be hub-like.

[0042] An upper image acquisition unit, that is, a first image acquisition unit, 86a, is attached to a lower section of the Z-axis motion plate 70a. Therefore, the upper image acquisition unit 86a is fixed in its position relative to the first cutting unit 78a. The upper image acquisition unit 86a is positioned above the clamping stage 10. The upper image acquisition unit 86a includes a microscope camera unit with an optical system comprising a condenser lens (not illustrated), etc., and an image acquisition device capable of photoelectrically converting visible light into electrical signals. The condenser lens has its optical axis substantially perpendicular to the surface 12a of the holding element 12.

[0043] Similarly, a second cutting unit 78b is attached to a lower section of the Z-axis motion plate 70b, positioned at the front in the +Y direction. The second cutting unit 78b includes a tubular spindle housing 80b, in which a section of a cylindrical spindle 82b (see Fig. 12) is rotatably mounted. The spindle 82b has one end coupled to a rotational mechanism (not illustrated), such as a servo motor, for rotating the spindle 82b about its central axis. A second cutting blade 84b with an annular cutting edge is attached to the other end of the spindle 82b. The second cutting blade 84b, in accordance with the present embodiment, is washer-like, i.e., of the hubless type, although it can also be hub-like.

[0044] The edge thickness, that is, a second thickness, 84b1 (see Fig. 12) of the second cutting edge 84b is less than the edge thickness, that is, a first thickness, 84a1 (see Fig. 8) of the first cutting blade 84a. Therefore, the width 13b1 of a second machining groove, i.e., a cutting groove, 13b, formed by the second cutting blade 84b in the workpiece 11 while cutting the workpiece 11, is smaller than the width 13a1 of a first machining groove, i.e., a cutting groove, 13a, formed by the first cutting blade 84a in the workpiece 11 while cutting the workpiece 11 (see Fig. 12 and Fig. 13) An upper image acquisition unit, that is, a second image acquisition unit, 86b, is attached to a lower section of the Z-axis motion plate 70b. Therefore, the upper image acquisition unit 86b is fixed in its position relative to the second cutting unit 78b. The upper image acquisition unit 86b is essentially identical in structure to the upper image acquisition unit 86a.

[0045] As in Fig. As illustrated in Figure 1, the base 4 also has a defined upwardly open opening 4d, which has a round shape and is positioned behind the opening 4b in the -Y direction. The opening 4d accommodates a cleaning unit 90 for cleaning a workpiece 11, etc., after it has been cut with a cleaning fluid, such as pure water. A housing (not illustrated) is arranged at the base 4. A touch panel 92, which serves as both an input panel and a display panel, is attached to a front side surface of the housing facing the +Y direction. The touch panel 92 displays images captured by the upper image acquisition unit 86a and 86b and the lower image acquisition unit 54.

[0046] As in the Fig. 10A and Fig. As illustrated in Figure 10B, the touch panel 92 displays an image 88a captured by the upper image acquisition unit 86a and a reference line 92a of the upper image acquisition unit 86a, generated by image processing. The reference line 92a is a straight line extending across the center of the image acquisition area of ​​the upper image acquisition unit 86a and essentially parallel to the X-axis directions. The upper image acquisition unit 86a serves as an eye, that is, a visual means, to confirm that an area of ​​the workpiece 11 has indeed been cut by the first cutting unit 78a. The reference line 92a corresponds to a line representing a target position where a first center line 13a2 (see Figure 10B) is located. Fig. 8) the first processing groove 13a is present.

[0047] As in the Fig. 14A and Fig. As illustrated in Figure 14B, the touch panel 92 similarly displays an image 88b, captured by the lower image acquisition unit 54, and a reference line 92b of the lower image acquisition unit 54, generated by image processing. Like reference line 92a, reference line 92b is a straight line extending across the center of the image acquisition area of ​​the lower image acquisition unit 54 and essentially parallel to the X-axis directions. The lower image acquisition unit 54 also serves as an eye, that is, a visual means, to confirm that an area of ​​the workpiece 11 is indeed to be cut by the second cutting unit 78b. Reference line 92b corresponds to a line representing a target position where a second center line 13b2 (see Figure 14B) is located. Fig. 12) the second processing groove 13b is present. The upper image acquisition unit 86a and the lower image acquisition unit 54 each have starting positions that are preset in accordance with each other. Therefore, the reference line 92a and the reference line 92b are also preset in accordance with each other and do not deviate from each other.

[0048] The touch panel 92 displays processing conditions, a graphical user interface (GUI), etc., as well as the images captured by the upper image acquisition units 86a and 86b and the lower image acquisition unit 54. The cutting device 2 includes a control unit 94 (see Fig. 1) for controlling the touch panel 92 etc. In particular, in addition to the touch panel 92, the control unit 94 controls the suction source 14, the X-axis movement mechanism 26, the rotary actuator 30, the Y-axis movement mechanism 32, the Z-axis movement mechanism 42, the lower image acquisition unit 54, the processing unit movement mechanism 60, the first cutting unit 78a, the second cutting unit 78b, the upper image acquisition units 86a and 86b, etc.

[0049] The controller 94 includes a computer with a processing unit, such as a processor of the type of a central processing unit (CPU), and a storage unit 96. The storage unit 96 has a main memory unit, such as a dynamic random access memory (DRAM), a static random access memory (SRAM), or a read-only memory (ROM), and an auxiliary memory unit, such as flash memory, a hard disk, or a solid-state drive. The auxiliary memory unit stores software, including predefined programs. The controller 94 performs its functions when the processing unit executes the software stored in the auxiliary memory unit. A cutting method, that is, a machining method, for cutting a workpiece 11 in accordance with a stepwise cutting operation using the cutting device 2 is described below.

[0050] Fig. Figure 7 is a flowchart of the machining process of a cutting method in accordance with a first embodiment of the present invention. To cut the workpiece 11, the end face 11a is inserted into the clamping table 10 with the belt 17 between them and held under tension, while the back face 11b is exposed upwards (holding step S10). If the workpiece 11 has not been cut along all projected parting lines 13 extending in a first direction (NO at step S20), then after holding step S10, machining grooves, i.e., first machining grooves 13a and second machining grooves 13b, are successively formed in the workpiece 11 by the first cutting blade 84a and the second cutting blade 84b (machining groove formation step).

[0051] The machining groove training step according to the present embodiment comprises steps S30 to S39, which are described below. In the machining groove training step, the lower image acquisition unit 54 acquires an image of the end face 11a of the workpiece 11, and an alignment operation is performed on the workpiece 11 based on the acquired image. Then, the rotary actuator 30 is activated to align the projected parting lines 13 substantially parallel to the X-axis directions, that is, an angular alignment operation is performed on the workpiece 11. Afterward, the first machining groove training step S30 is performed. Fig. Figure 8 illustrates the first machining groove formation step S30 in section. In the first machining groove formation step S30, an initial cutting position is determined to place the first cutting blade 84a along a projected parting line 13 and to position the lower end of the first cutting blade 84a at a predetermined depth 23 between the end face 11a and the back face 11b. The X-axis motion table 18 is then moved for machining, causing the first cutting blade 84a to form a first machining groove 13a, i.e., a half-cut groove, in the workpiece 11 to the predetermined depth 23, which ends just before the end face 11a. The depth 23 is not limited to half the thickness of the workpiece 11 but can be set to any desired depth depending on the workpiece.

[0052] After the first machining groove 13a has been formed in the workpiece 11, the upper image acquisition unit 86a takes an image of the first machining groove 13a, which is exposed on the back side 11b, using visible light (first image acquisition step S31). Fig. Figure 9 illustrates a first image acquisition step S31 of the cutting process in section. After the first image acquisition step S31, the control unit 94 detects a deviation of the first center line 13a2 of the first machining groove 13a from the reference line 92a (first machining groove verification step S32). The first center line 13a2 is positioned in the middle of the width of the machining groove 13a and extends essentially parallel to the X-axis directions. The first center line 13a2 corresponds essentially to a center 84a2 in width (see Figure 9). Fig. 8) the cutting edge of the first cutting blade 84a when the first cutting blade 84a cuts the workpiece 11 to form the first machining groove 13a in the workpiece 11.

[0053] Fig. Figure 10A illustrates an example of an image that includes the first editing groove 13a. In Fig. In step 10A, the first center line 13a2 and the reference line 92a are positioned aligned with each other in the Y-axis directions. In this case, that is, in the case of a YES at step S32, the control proceeds to an additional first machining groove training step S34.

[0054] Before the workpiece 11 is cut, a process is performed to align the first centerline 13a2 and the reference line 92a, i.e., a fine-tuning process, using a mirror wafer or similar device. Therefore, the first centerline 13a2 and the reference line 92a are normally aligned before the workpiece 11 is cut. However, in a case where the workpiece 11 is made of a hard material or is relatively thick, or the direction along which the workpiece 11 is cut is inclined with respect to a direction tangential to a point on the outer circumferential edge of the workpiece 11, the first centerline 13a2 may deviate from the reference line 92a.

[0055] Fig. Figure 10B illustrates another example of an image that includes the first editing groove 13a. In Fig. In 10B, a deviation distance and direction by which, or in which, the first center line 13a2 deviates from the reference line 92a in the Y-axis directions are indicated by a vector B1. If, during the first cut groove inspection step S32, the deviation distance is greater than a predetermined limit, for example 5 µm, the controller 94 then generates an alarm sound via a loudspeaker (not illustrated) or displays an alarm message on the touch panel 92, prompting an operator to perform the fine-tuning procedure.

[0056] The operator uses the touch panel 92 to actuate the respective processing unit movement mechanism 60 while viewing image 88a. This moves the upper image acquisition unit 86a in one of the Y-axis directions to align the reference line 92a with the first center line 13a2 (first fine-tuning step S33). To perform a high-precision cutting operation, the operator can confirm image 88a and, if necessary, perform a first fine-tuning step S33, regardless of whether an alarm is triggered during the first kerf verification step S32.

[0057] Based on a distance and direction by which, or in which, the upper image acquisition unit 86a is moved during the first fine-tuning step S33, the control unit 94 detects a deviation distance and a deviation direction of the upper image acquisition unit 86a, that is, the deviation in Fig. 10B illustrated vector B1, and stores the detected deviation distance and deviation direction in the storage device 96. When the first cutting blade 84a cuts the workpiece 11 after the first fine-tuning step S33, the control 94 corrects the position of the center 84a2 of the first cutting blade 84a to compensate for the deviation distance and deviation direction.

[0058] In an additional first machining groove formation step S34, the first cutting units 78a are positioned by a predetermined road division. The first cutting blade 84a is thus positioned on an adjacent projected parting line 13 and forms a first machining groove 13a in the workpiece 11 in a similar manner. In the additional first machining groove formation step S34, several, or in particular four, first machining grooves 13a are formed in the workpiece 11. Fig. Figure 11 illustrates the additional first machining groove formation step S34 in section. In this way, five first machining grooves 13a are formed in the workpiece 11 in steps S30 to S34.

[0059] After an additional first machining groove training step S34, a second cutting position is determined, corresponding to the first cutting position, to place the second cutting blade 84b on an extension of the first machining groove 13a, which was formed during the first machining groove training step S30, and to position the lower end of the second cutting blade 84b, which rotates at high speed, between the end face 11a and the surface 12a. Then the X-axis motion table 18 is moved for machining, forming a second machining groove 13b that extends to the end face 11a (second machining groove training step S35). Fig. Figure 12 illustrates the second machining groove formation step S35 in section. In the second machining groove formation step S35, the workpiece 11 is divided along a first machining groove 13a and a second machining groove 13b. After the second machining groove formation step S35, the lower image acquisition unit 54, for example the high-magnification camera 58 and the illumination device 58a, takes an image of the second machining groove 13b, which is formed in the end face 11a, with visible light through the clamping table 10 (second image acquisition step S36).

[0060] Fig. Figure 13 illustrates the second image acquisition step S36 in section. Since, in accordance with the present embodiment, the lower image acquisition unit 54 captures an image of the second machining groove 13b instead of the upper image acquisition units 86a and 86b, it is always possible to capture an image of the second machining groove 13b. After the second image acquisition step S36, the control unit 94 detects a deviation of the second center line 13b2 of the second machining groove 13b from the reference line 92b (second machining groove verification step S37). The second center line 13b2 is positioned at the midpoint of the width of the second machining groove 13b and extends substantially parallel to the X-axis directions. The second center line 13b2 corresponds substantially to a center 84b2 in the width direction (see Figure 13). Fig. 12) the cutting edge of the second cutting blade 84b when the second cutting blade 84b cuts the workpiece 11 to form the second machining groove 13b in the workpiece 11. Fig. Figure 14A illustrates an example of an image that includes the second editing groove, 13b. Fig. In step 14A, the second center line 13b2 and the reference line 92b are positioned aligned with each other in the Y-axis directions. In this case, that is, in the case of a YES at step S37, the control proceeds to the additional second machining groove training step S39.

[0061] The second centerline 13b2 and the reference line 92b are normally aligned. However, in a case where the workpiece 11 is made of a hard material or for other reasons described above, the second centerline 13b2 may deviate from the reference line 92b. Fig. Figure 14B illustrates another example of an image that incorporates the second editing groove, 13b. Fig. In 14B, a deviation distance and direction by which, respectively, the second center line 13b2 deviates from the reference line 92b in the Y-axis directions are indicated by a vector B2.

[0062] If the deviation during the second groove verification step S37 exceeds a predetermined limit, such as 5 µm, the controller 94 triggers an alarm, prompting the operator to perform the fine-tuning procedure. The operator uses the touch panel 92 to actuate the respective processing unit movement mechanism 60 while viewing image 88b. This moves the lower image acquisition unit 54 in one of the Y-axis directions to align the reference line 92b with the second center line 13b2 (second fine-tuning step S38). To perform a high-precision cutting operation, the operator can acknowledge image 88b and, if necessary, execute a second fine-tuning step S38 regardless of whether an alarm was triggered during the second groove verification step S37.

[0063] Based on a distance and direction by which, or in which, the lower image acquisition unit 54 is moved during the second fine-tuning step S38, the control unit 94 detects a deviation distance and direction of deviation of the lower image acquisition unit 54, that is, the deviation in Fig. 14B illustrated vector B2, and stores the detected deviation distance and deviation direction in the storage device 96. When the second cutting blade 84b cuts the workpiece 11 after the fine-tuning step S38, the controller 94 corrects the position of the center 84b2 of the second cutting blade 84b to compensate for the deviation distance and deviation direction.

[0064] In accordance with the present embodiment, the first cutting groove verification step S32 and the second cutting groove verification step S37 are collectively referred to as the acquisition step. During the acquisition step, it is possible to detect whether the position of the first center line 13a2, obtained during the first image acquisition step S31, and the position of the second center line 13b2, obtained during the second image acquisition step S36, coincide in an XY plane, that is, a predetermined plane. In a case where at least one of the first fine-tuning step S33 and the second fine-tuning step S38 is performed, it is determined that the first center line 13a2 and the second center line 13b2 do not coincide during the acquisition step.In accordance with the present embodiment, the first fine-tuning step S33 and the second fine-tuning step S38, each performed as necessary, are referred to together as a correction step. When the correction step is performed, the center 84a2 of the first cutting blade 84a is aligned via its edge thickness 84a1, and the center 84b2 of the second cutting blade 84b is aligned via its edge thickness 84b1.

[0065] After step S37 or steps S37 and S38, second machining grooves 13b are formed in a similar manner in the workpiece 11 below the remaining four first machining grooves 13a (additional second machining groove formation step S39). Fig. Figure 15 illustrates the workpiece 11 in section after an additional second machining groove training step S39 has been carried out.

[0066] The control then returns to step S20. If step S20 is marked NO, the steps from the first machining groove formation step S30 to the additional second machining groove formation step S39 are executed again. In this way, the workpiece 11 is cut along all projected parting lines 13 in the first direction, after which the clamping table 10 is rotated 90° about its central axis. Then, the workpiece 11 is cut in a similar manner along all projected parting lines 13 extending along a second direction perpendicular to the first direction. After the workpiece 11 has been cut along all projected parting lines 13 extending along both the first and second directions (YES in step S20), the entire cutting process comes to an end.

[0067] If the position of the first center line 13a2 and the position of the second center line 13b2 in the XY plane do not coincide, then, in accordance with the first embodiment, at least one of the positions of the center 84a2 of the first cutting blade 84a and the center 84b2 of the second cutting blade 84b is corrected to bring the position of the first center line 13a2 and the position of the second center line 13b2 into agreement during the correction step, i.e., steps S33 and S38. When the workpiece 11 is cut after the correction step, the first center line 13a2 of the first machining groove 13a on the back side 11b and the second center line 13b2 of the second machining groove 13b on the front side 11a are kept in agreement with each other. The cutting process is particularly effective when the workpiece 11 is cut in stages. (First variation)

[0068] In the first machining groove formation step S30, only one first machining groove 13a can be formed in the workpiece 11 instead of several first machining grooves 13a. The first machining groove 13a does not have to be formed in a component area where the components 15 are formed, but in an outer circumferential excess area that exists around the component area. (Second variation)

[0069] In accordance with the first embodiment, the edge thickness 84b1 of the second cutting blade 84b is smaller than the edge thickness 84a1 of the first cutting blade 84a. However, the edge thickness 84b1 can be the same as the edge thickness 84a1. (Second embodiment)

[0070] A second embodiment of the present invention is described below with reference to the Fig. 16A and Fig. 16B described. A cutting device 2 in accordance with the second embodiment has a lower image acquisition unit, that is, a third image acquisition unit, 100 (see Fig. 16A and Fig. 16B), which is capable of capturing an image of the workpiece 11 using infrared radiation, instead of the lower image acquisition unit 54. The lower image acquisition unit 100 also includes a microscope camera unit comprising a low-magnification camera and a high-magnification camera. Each camera has an image acquisition device capable of photoelectrically converting infrared radiation into electrical signals. Each camera is combined with an associated illumination device for applying infrared beams, such as near-infrared beams.

[0071] In accordance with the second embodiment, the cutting device 2 also cuts the workpiece 11 in accordance with the one described in Fig. Figure 7 illustrates the processing sequence. However, the second embodiment differs from the first embodiment in that both the first image acquisition step S31 and the second image acquisition step S36 are performed using the lower image acquisition unit 100. Fig. Figure 16A illustrates in section a first image acquisition step S31 of a cutting process in accordance with the second embodiment. In the first image acquisition step S31, the image acquisition device captures an image of the first processing groove 13a, which is formed in the back side 11b, using infrared radiation, while the camera is focused at high magnification through the clamping table 10 onto the back side 11b. Fig.Figure 16B illustrates in section a second image acquisition step S36 of the cutting process in accordance with the second embodiment. In the second image acquisition step S36, the image acquisition device captures an image of the second processing groove 13b, which is formed in the end face 11a, using infrared radiation, while the camera is focused at high magnification through the clamping table 10 onto the end face 11a.

[0072] Even if the first center line 13a2 and the second center line 13b2 differ from each other, in accordance with the second embodiment, as in the first embodiment, the first center line 13a2 of the first machining groove 13a on the back side 11b and the second center line 13b2 of the second machining groove 13b on the front side 11a can be aligned when the workpiece 11 is cut after the correction step. Structural details, process details, and other details in accordance with the above embodiments of the present invention can be appropriately modified or adapted without departing from the scope of protection of the invention. The modifications of the first embodiment described above can be applied to the second embodiment.

Claims

[1] Method for machining a workpiece (11) comprising: a holding step (S10) for holding an end face (11a) of the workpiece (11) on a holding table (10) which has an area made of a transparent material, while a rear face (11b) of the workpiece (11) is exposed; and a machining groove training step (S30, S35) involving the training of a machining groove (13a) in the workpiece (11) by cutting the workpiece (11) held on the holding table (10) with a cutting blade (84a, 84b), where the processing groove training step (S30) exhibits: a first image acquisition step (S31) by taking an image of the machining groove (13a) on the back (11b) of the workpiece (11), a second image acquisition step (S36) with an image of the machining groove (13a) on the end face (11a) of the workpiece (10) being taken through the holding table (10), and a capture step (S32, S37) with a capture of whether a position of a first center line (13a2) of the processing groove (13a), whose image was captured in the first image acquisition step (S31), and a position of a second center line (13b2) of the processing groove (13a), whose image was captured in the second image acquisition step (S36), coincide in a predetermined plane or not, and If the position of the first center line (13a2) and the position of the second center line (13b2) do not match in the predetermined plane during the capture step (S32, S37), then the machining groove training step (S30) further includes a correction step (S33, S38) with a correction of a position of a center of the cutting blade (84a) to bring the position of the first center line (13a2) and the position of the second center line (13b2) into agreement. [2] Method for machining a workpiece (11) according to claim 1, wherein the machining groove formation step (S30, S35) comprises: a first machining groove formation step (S30) comprising forming a first machining groove (13a) in the workpiece (11) with a first cutting blade (84a) having a first thickness (84a1), wherein the first machining groove (13a) has a predetermined depth (23) to just before the end face (11a), and a second machining groove formation step (S35) comprising positioning a second cutting blade (84b) having a second thickness (84b1) at the first machining groove and forming a second machining groove (13b) in the workpiece (11) along the first machining groove (13a), the second machining groove (13b) extending to the end face (11a), thereby dividing the workpiece. [3] Method for machining a workpiece (11) according to claim 2, wherein the second cutting blade (84b) has a narrower edge thickness than the first cutting blade (84a). [4] Method for machining a workpiece (11) according to claim 2 or 3, wherein the first image acquisition step comprises taking an image of the first processing groove (13a) on the back (11b) with visible light using a first image acquisition unit (86a) positioned above the workpiece (11), the second image acquisition step comprises taking an image of the second machining groove (13b) on the end face (11a) through the holding table (10) using visible light and a second image acquisition unit (54) arranged under the workpiece (11), and The detection step includes detecting whether the position of a first center line (13a2) of the first machining groove (13a) on the back (11b) and the position of a second center line (13b2) of the second machining groove (13b) on the front (11a) coincide in the predetermined plane. [5] Method for machining a workpiece (11) according to any one of claims 2 to 4, wherein the first image acquisition step comprises taking an image of the first machining groove (13a) on the back (11b) with infrared radiation through the holding table (10) using a third image acquisition unit (100) which is arranged under the workpiece (11), the second image acquisition step comprises capturing an image of the second processing groove (13b) on the front face (11a) with infrared radiation through the holding table (10) using the third image acquisition unit (100), and The detection step includes detecting whether the position of a first center line (13a2) of the first machining groove (13a) on the back and the position of a second center line (13b2) of the second machining groove (13b) on the front (11a) coincide in the predetermined plane or not.

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