JP6302732B2 - Cutting method - Google Patents

Description

  The present invention relates to a cutting method for cutting a workpiece held on a chuck table with a cutting blade.

  2. Description of the Related Art Conventionally, in a cutting method of cutting a workpiece such as a semiconductor wafer, the workpiece is cut by relatively reciprocating a workpiece held on a chuck table and a chuck table rotated at high speed. The cutting blade is formed by solidifying diamond abrasive grains with a binder such as electroforming bond. In cutting using a cutting blade, the binder is consumed during processing, and the abrasive grains that contributed to the cutting fall off, and new abrasive grains are exposed from the surface of the blade (self-generated blades). It continues well (see, for example, Patent Document 1).

JP 2010-000588 A

  By the way, as a work piece, a part in which a metal pattern called a TEG (Test Element Group) is partially arranged on a planned division line has been put into practical use. When cutting such a workpiece with TEG, there is a possibility that clogging may occur locally on the processed surface of the cutting blade. When a workpiece is cut with such a cutting blade, there is a problem that the machining quality of the workpiece is locally deteriorated.

  This invention is made | formed in view of such a point, and it aims at providing the cutting method which can prevent the deterioration of the local processing quality which arises in the middle of continuous cutting.

The cutting method of the present invention cuts a workpiece by a cutting means having a spindle that is rotatably supported, a motor that rotationally drives the spindle, and a cutting blade attached to the tip of the spindle. A cutting method for holding a workpiece on a chuck table, and after performing the holding step, a predetermined cut is made while rotating the cutting blade with respect to the workpiece held on the chuck table. A machining step positioned at a position and cutting the workpiece by cutting and feeding the chuck table and the cutting blade at a predetermined speed relative to each other, and a load of the motor of the spindle during the machining step. comprising a detection step of detecting a current value, and in the processing step, when the load current value of the motor exceeds a predetermined threshold value, said during cutting Down to a slower speed than the constant speed, by interposing midway performing precut step a precut for cutting the workpiece stepwise increased from the slow speed until the predetermined speed, characterized by.

  According to this configuration, the load on the spindle due to clogging of the cutting blade or the like is monitored based on the load current value of the spindle motor during cutting. For this reason, when the load current value of the motor exceeds a predetermined threshold value, it is determined that the machining quality of the workpiece starts to deteriorate, and the precut is performed. In the pre-cut, the cutting feed speed is reduced, so that the water circumference of the cutting blade is improved, and the cutting process is continued with the spindle load reduced to promote the self-generated blade. Thereafter, the cutting feed speed is gradually increased to raise the workpiece to a predetermined speed. In this way, since the pre-cut is interposed during the cutting process, clogging of the cutting blade is eliminated and the cutting ability is restored, thereby preventing local deterioration of the processing quality of the workpiece. it can. Further, since the machining quality of the workpiece is monitored from the load current value of the spindle motor, the cutting process can be continued without performing work such as kerf check.

  According to the present invention, the load current value of the spindle motor is monitored and the pre-cut is interposed during the cutting process, so that local machining quality deterioration caused during the continuous cutting process is prevented. Can be prevented.

It is a perspective view of the cutting device concerning this embodiment. It is a figure which shows the relationship between the cutting which concerns on this Embodiment, and load current value. It is a figure which shows an example of the setting conditions of the precut mode which concerns on this Embodiment. It is operation | movement explanatory drawing of the cutting method which concerns on this Embodiment.

  Hereinafter, embodiments will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a cutting apparatus according to the present embodiment. The cutting device used in the cutting method according to the present embodiment is not limited to the configuration shown in FIG. The cutting device used in the cutting method according to the present embodiment only needs to be configured so that a precut can be interposed during the cutting process, and may be a cutting device provided with a pair of cutting blades, for example.

  As shown in FIG. 1, the cutting apparatus 1 divides the workpiece W into individual chips by moving the cutting blade 41 of the cutting means 4 relative to the workpiece W on the chuck table 3. It is configured. The surface 71 of the workpiece W is provided with a grid-like division planned line 72 (see FIG. 2), and various devices D are formed in each region partitioned by the division planned line 72. A dicing tape T is attached to the back surface of the workpiece W, and an annular frame F is attached to the outer periphery of the dicing tape T. The workpiece W is carried into the cutting device 1 while being supported by the annular frame F via the dicing tape T.

  The workpiece W may be a semiconductor wafer in which devices such as IC and LSI are formed on a semiconductor substrate such as silicon and gallium arsenide, or an optical device such as an LED on a ceramic, glass, and sapphire inorganic material substrate. It may be a formed optical device wafer.

  A chuck table moving mechanism 5 that moves the chuck table 3 in the X-axis direction is provided on the base 2 of the cutting apparatus 1. The chuck table moving mechanism 5 includes a pair of guide rails 51 arranged on the base 2 and parallel to the X-axis direction, and a motor-driven X-axis table 52 slidably installed on the pair of guide rails 51. doing. A nut portion (not shown) is formed on the back side of the X-axis table 52, and a ball screw 53 is screwed to the nut portion. Then, the drive motor 54 connected to one end of the ball screw 53 is rotationally driven, whereby the chuck table 3 is moved along the guide rail 51 in the X-axis direction.

  The chuck table 3 is rotatably provided on the X-axis table 52 via a θ table 55. On the upper surface of the chuck table 3, a holding surface 31 is formed of a porous ceramic material. The holding surface 31 is connected to a suction source (not shown) through a flow path in the chuck table 3, and the workpiece W is sucked and held by the negative pressure generated on the holding surface 31. Four clamp portions 32 are provided around the chuck table 3 via a pair of support arms. Each clamp part 32 is driven by an air actuator (not shown), so that the annular frame F around the workpiece W is clamped and fixed from four directions.

  On the base 2 of the cutting apparatus 1, a cutting means moving mechanism 6 for moving the cutting means 4 in the Y-axis direction and the Z-axis direction above the chuck table 3 is provided. The cutting means moving mechanism 6 has a pair of guide rails 61 arranged on the base 2 and parallel to the Y-axis direction, and a motor-driven Y-axis table 62 slidably installed on the pair of guide rails 61. doing. The Y-axis table 62 is formed in a rectangular shape when viewed from above, and a side wall 65 is erected at one end of the Y-axis table 62 in the X-axis direction.

  Further, the cutting means moving mechanism 6 includes a pair of guide rails 66 (only one shown) installed on the wall surface of the side wall portion 65 and parallel to the Z-axis direction, and a Z slidably installed on the pair of guide rails 66. And an axis table 67. Nut portions (not shown) are formed on the back sides of the Y-axis table 62 and the Z-axis table 67, and ball screws 63 and 68 are screwed into these nut portions. The drive motors 64 and 69 connected to one end of the ball screws 63 and 68 are rotationally driven, so that the cutting means 4 is moved along the guide rails 61 and 66 in the Y-axis direction and the Z-axis direction.

  The Z-axis table 67 is provided with cutting means 4 having a cutting blade 41 attached to the tip of the spindle 42. The spindle 42 is rotatably supported in a spindle case 43 extending from the Z-axis table 67 in the Y-axis direction, and is rotated by a motor 44 in the spindle case 43. As the cutting blade 41, for example, an electroforming blade in which diamond abrasive grains are hardened with an electroforming bond to form a circle is selected. The cutting blade 41 is covered with a blade cover 45, and the blade cover 45 is provided with an injection nozzle 46 for injecting cutting water toward the cutting portion.

  The spindle case 43 is provided with an image pickup means 7 for alignment for picking up an image of the surface 71 of the workpiece W held on the chuck table 3. 2), the cutting blade 41 is aligned. In the cutting means 4, the workpiece W is cut along the scheduled division line 72 by the cutting blade 41 rotated at high speed while cutting water is jetted from the plurality of jet nozzles 46 to the cutting portion. The cutting means 4 is connected to a power supply source 47 that supplies power to the motor 44 of the spindle 42 and load current value detection means 48 that detects the load current value of the motor 44.

  Further, the cutting device 1 is provided with a control means 9 that performs overall control of each part of the device. The control means 9 includes a processor that executes various processes, a memory, and the like. The memory is composed of one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application. The memory stores not only processing conditions for mass production of the cutting device 1 but also processing conditions for pre-cutting. Pre-cut is a method in which machining is started from a feed speed slower than that of mass production until the machining quality of the cutting process is stabilized, and the feed speed is gradually increased to the feed speed for mass production. It is.

  Usually, in the cutting device 1, the state of the cutting groove such as the size of chipping is periodically checked by a kerf check, thereby preventing the processing quality from being deteriorated. However, a periodic kerf check can recognize the deterioration of the machining quality only at the timing of the kerf check. Therefore, in the present embodiment, paying attention to the fact that the load current value of the motor 44 of the spindle 42 increases when the machining quality deteriorates during the cutting process, the load current value of the motor 44 exceeds a predetermined threshold value. At this point, the pre-cut mode is entered.

  Hereinafter, the precut mode will be described with reference to FIGS. FIG. 2 is a diagram showing the relationship between the cutting process and the load current value according to the present embodiment. FIG. 3 is a diagram illustrating an example of setting conditions for the precut mode according to the present embodiment.

  As shown in FIG. 2, electric power is supplied from the power supply source 47 to the motor 44 of the spindle 42 during the cutting process, and the load current value generated by the motor 44 during the cutting process of the workpiece W is the load current value. It is detected by the detecting means 48. In this case, even when the load acting on the spindle 42 (motor 44) increases due to clogging or the like, the load current value fluctuates so as to rotate the spindle 42 with a constant torque under a constant voltage. By monitoring this, a decrease in the cutting ability of the cutting blade 41 is detected. In the control means 9, the load current value is compared with the predetermined threshold value, and when the load current value exceeds the predetermined threshold value, the pre-cut mode is entered, and the feed by the drive motor 54 of the chuck table 3 (see FIG. 1). Controlled to slow down.

  For example, in the cutting process shown in FIG. 2, the cutting blade 41 is clogged at a position P in the middle of the second scheduled division line 72 of the workpiece W from the lower side of the paper surface, and the load is applied during the cutting process. The current value increases so as to exceed a predetermined threshold. Thereafter, since the load current value of the motor 44 fluctuates at a high level near the threshold value, the workpiece W is cut in the pre-cut mode from the next scheduled division line 72 in the third column. As a result, the speed is reduced from the normal cutting feed speed (for example, 70 [mm / s]), and the cutting process is continued at a low cutting feed speed (for example, 10 [mm / s]). Load current value falls below a predetermined threshold.

  As shown in FIG. 3, in the pre-cut mode, the cutting feed speed is set to six stages, and cutting is performed while increasing the stage from the first stage to the sixth stage. The cutting feed speed and the number of cutting lines (the number of lines to be divided 72) are associated with each stage, and the first stage is 10 [mm / s], 20 lines, and the second stage is 20 [mm]. / S] 10 lines, 3rd stage 30 [mm / s] 10 lines, 4th stage 40 [mm / s] 20 lines, 5th stage 50 [mm / s] 20 lines, 6 The stage is set to 20 lines at 60 [mm / s]. When cutting is completed under the sixth stage of processing conditions, the processing conditions are restored to those for mass production of the product, and the processing is continued at a normal cutting feed rate of 70 [mm / s].

  Thus, by shifting to the pre-cut mode and reducing the cutting feed speed, the water around the cutting blade 41 is improved and clogging is eliminated, and the load on the spindle 42 (cutting blade 41) is reduced. By continuing the cutting process in this state, the cutting blade 41 is urged to self-generate and the cutting ability is recovered. Further, since the load current value of the motor 44 of the spindle 42 is monitored, not only the timing of the kerf check but also the deterioration of the machining quality during the cutting process is recognized, and the precut is performed during the cutting process. For this reason, local deterioration of processing quality that occurs during continuous cutting is prevented.

  In addition, the processing conditions at the time of precut and the predetermined threshold value of the load current value can be set as appropriate, and may be set for each product (for each IDNo) and for each cutting blade. In addition, although the cutting feed speed is set to 6 stages as the processing conditions at the time of pre-cutting, it may be set to 5 stages or less, or may be set to 7 stages or more.

  The operation of the cutting method according to the present embodiment will be described with reference to FIG. FIG. 4 is an operation explanatory diagram of the cutting method according to the present embodiment. 4A shows a holding step, FIG. 4B shows a processing step and a detection step, and FIG. 4C shows a precut step. FIG. 4 shows an example in which the machining load of the cutting blade increases during the machining of the workpiece.

  As shown in FIG. 4A, in the holding step, the workpiece W is held on the holding surface 31 of the chuck table 3 (see FIG. 1) via the dicing tape T. Then, the workpiece W on the chuck table 3 is positioned below the cutting blade 41.

  As shown in FIG. 4B, the processing step is performed after the holding step is performed. In the processing step, the cutting blade 41 is aligned with the planned division line 72 in a state where the cutting blade 41 is positioned outside the outer peripheral edge of the workpiece W. The cutting blade 41 is lowered to a predetermined cutting position outside the workpiece W and the dicing tape T is cut while the cutting blade 41 is rotated while the cutting water is jetted from the jet nozzle 46 (see FIG. 1). . When the dicing tape T is cut to a predetermined depth by the cutting blade 41, the chuck table 3 (see FIG. 1) is cut and fed relative to the cutting blade 41 in the X-axis direction. Thereby, the workpiece W is cut along the scheduled division line 72 by the cutting blade 41. At this time, the machining conditions at the time of mass production are set as the machining conditions at the time of cutting, and the cutting feed speed of the cutting blade 41 is set to a predetermined speed (for example, 70 [mm / s]).

  In addition, a detection step is performed during the processing step. In the detecting step, the load current value detecting means 48 detects the load current value of the motor 44 of the spindle 42. The detection result of the load current value detection means 48 is output to the control means 9, and the control means 9 compares the load current value of the motor 44 with a predetermined threshold value. If the load current value of the motor 44 of the spindle 42 exceeds a predetermined threshold value in the machining step, it is determined that the cutting ability of the cutting blade 41 has decreased, and the precut step is performed in the middle of the machining step. The machining step is continued until the load current value of the motor 44 exceeds a predetermined threshold value.

  As shown in FIG. 4C, in the pre-cut step, the setting is changed from a predetermined cutting feed speed of the cutting blade 41 to a cutting feed speed (for example, 10 [mm / s]) lower than the predetermined speed. Then, pre-cutting is started from the next division line 72 at a low cutting feed speed after the setting change. As a result, the processing load on the cutting blade 41 is reduced, and the load current value detected by the load current value detecting means 48 falls below a predetermined threshold value. At this time, the water circumference of the cutting blade 41 is improved, the clogging of the processed surface of the cutting blade 41 is improved by the discharge action of the cutting waste, and the cooling effect at the cutting location of the workpiece W is enhanced. By continuing the cutting process in this state, the self-generated blade of the cutting blade 41 is promoted, and the cutting blade 41 is brought close to a normal condition.

  Then, the remaining divided lines 72 are also cut while being gradually increased from a low speed during pre-cutting to a predetermined speed during mass production. As described above, the speed is increased by one step (for example, in units of 10 [mm / s]) every time a predetermined number of the division planned lines 72 are processed at six stages of cutting feed speeds. If all the planned division lines 72 of the workpiece W have been cut before the cutting feed speed returns to the predetermined speed at the time of product mass production, the precut is continued for the new workpiece W. On the other hand, when the cutting feed speed reaches a predetermined speed at the time of mass production, the cutting blade 41 is returned to the processing step from the pre-cut step while the cutting ability of the cutting blade 41 is recovered, and the cutting process is continued.

  In the present embodiment, when the load current value exceeds a predetermined threshold, the pre-cut step is started from the next scheduled division line 72. However, the present invention is not limited to this configuration. The precut step may be started immediately after the load current value exceeds a predetermined threshold.

  As described above, according to the present embodiment, the load on the spindle 42 due to clogging of the cutting blade 41 or the like is monitored by the load current value of the motor 44 of the spindle 42 during the cutting process. For this reason, when the load current value of the motor 44 exceeds a predetermined threshold value, it is determined that the machining quality of the workpiece W starts to deteriorate, and the precut is performed. In the pre-cut, the cutting feed speed is reduced, so that the water circumference of the cutting blade 41 is improved, and the cutting process is continued in a state where the load on the spindle 42 is reduced, and the self-generated blade is promoted. Thereafter, the cutting feed speed is gradually increased, and the workpiece W is increased to a predetermined speed. As described above, the precut is interposed during the cutting process, so that the clogging and the like of the cutting blade 41 is eliminated, the cutting ability is recovered, and the local processing quality of the workpiece W is prevented from being deteriorated. . Further, since the machining quality of the workpiece W is monitored from the load current value of the motor 44 of the spindle 42, the cutting process can be continued without performing a work such as a kerf check.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, the chuck table 3 is moved with respect to the cutting blade 41 and cut and fed. However, the present invention is not limited to this configuration. Any configuration in which the chuck table 3 and the cutting blade 41 are moved relative to each other may be used, and for example, the cutting blade 41 may be moved relative to the chuck table 3 to perform cutting feed.

  In the above-described embodiment, the detection step is performed during the processing step. However, the present invention is not limited to the configuration in which the detection step is always performed during the processing step. The detection step may be performed periodically during the processing step.

  In the above-described embodiment, when the load current value of the motor 44 of the spindle 42 exceeds a predetermined threshold value, the speed is gradually increased from the slowest speed among the six stages of cutting feed speeds. However, the present invention is not limited to this configuration. The initial speed of the precut can be appropriately changed according to the material of the workpiece W or the like.

  As described above, the present invention has an effect that it is possible to prevent local deterioration of processing quality that occurs during continuous cutting, and in particular, to cut a workpiece with TEG. Useful for cutting methods.

DESCRIPTION OF SYMBOLS 1 Cutting device 3 Chuck table 4 Cutting means 9 Control means 41 Cutting blade 42 Spindle 44 Motor 47 Power supply source 48 Load current value detection means W Workpiece

Claims (1)

A cutting method for cutting a workpiece with a cutting means having a spindle rotatably supported, a motor for rotationally driving the spindle, and a cutting blade attached to the tip of the spindle,
A holding step for holding the workpiece on the chuck table;
After carrying out the holding step, the cutting blade is rotated and positioned at a predetermined cutting position with respect to the workpiece held on the chuck table, and the chuck table and the cutting blade are cut at a predetermined speed relatively. Processing steps to feed and cut the workpiece;
A detection step of detecting a load current value of the motor of the spindle during the processing step;
The In processing step, when the load current value of the motor exceeds a predetermined threshold value, dropping to a slower speed than the predetermined speed during cutting, increased stepwise from the slow speed until the predetermined velocity And a pre-cut step for performing pre-cut for cutting the workpiece.

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