Wire saw device and method for cutting workpieces

Abstract

The wire saw device (1) comprises a swinging mechanism (30) that swings the workpiece W, a lifting mechanism (4) that supports the swinging mechanism so that it can move up and down, a wire drive mechanism (5) that rotates a pair of wire guides (2,2) to move the cutting wire (3) back and forth, and a control device (20) that controls the swinging mechanism, the lifting mechanism and the wire drive mechanism. The control device controls the wire saw device (1) so that the workpiece and the cutting wire always make contact at one point on the arc of the workpiece, while keeping the swinging center of the workpiece at or near the center of the cross-sectional shape of the workpiece.

Description

Technical Field

[0001] The present invention relates to a wire saw apparatus for cutting a workpiece (hereinafter referred to as a work), such as a silicon ingot, and a method for cutting the work.

Background Art

[0002] Conventionally, a wire saw apparatus has been used as a means for cutting a thin plate-shaped wafer from a work. In the wire saw apparatus, while running a cutting wire wound spirally around a plurality of wire guides, the work is pressed against the cutting wire, and the work is simultaneously cut at a plurality of locations.

[0003] Also, for example, in the wire saw apparatus disclosed in Patent Document 1, while running a cutting wire wound spirally around a plurality of wire guides and swinging the cutting wire together with the wire guides, a wire saw apparatus is known in which a workpiece is pressed against the cutting wire to perform a cutting process on the workpiece. In this wire saw apparatus, the position of the holding means for holding the workpiece is controlled according to the swing angle of the cutting wire so that the workpiece has an arc-shaped processing shape. By doing so, compared with the case where the cutting wire is not swung, the contact distance between the work and the cutting wire becomes shorter, so that the grinding force can be increased to increase the cutting speed, and the chip discharge property can be improved to improve the processing accuracy.

[0004] A similar effect can also be obtained in a type of wire saw apparatus (see, for example, Patent Documents 2 and 3) that performs cutting of a work while swinging the work.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] However, in recent years, workpieces have become larger in diameter, and there is a need to improve cutting speed and reduce the rate of wire breakage even for such large workpieces.

[0007] The present invention has been made in view of the above, and its purpose is to improve the cutting speed and reduce the rate of wire breakage in a wire saw device, in response to the increasing diameter of the workpiece. [Means for solving the problem]

[0008] To achieve the above objective, this invention is designed to cut a workpiece while maintaining the pivot point of the workpiece in an appropriate position.

[0009] Specifically, the wire saw device of the first invention is A rocking mechanism that supports the workpiece in a rocking manner, A lifting mechanism that supports the aforementioned rocking mechanism so that it can move up and down, A wire drive mechanism that rotates a pair of wire guides to move the cutting wire back and forth, The system includes a control device for controlling the rocking mechanism, the lifting mechanism, and the wire drive mechanism.

[0010] The control device then controls the workpiece to oscillate using the oscillating mechanism while maintaining the oscillating center of the workpiece at or near the center of the cross-sectional shape of the workpiece, so that the workpiece and the cutting wire always come into contact at one point on the arc of the workpiece.

[0011] According to the above configuration, the workpiece is brought close to the cutting wire, which moves back and forth via a wire drive mechanism, by a lifting mechanism to cut the workpiece. During processing, the workpiece is pressed against the cutting wire while being oscillated by the oscillating mechanism, improving chip evacuation. Furthermore, the length of the cutting wire in contact with the processing area is shortened, resulting in concentrated and consistently uniform force, thus improving processing efficiency and accuracy (roughness, thickness, waviness, etc.). In addition, since the center of oscillation of the workpiece is positioned at or near the center of the cross-sectional shape of the workpiece, the oscillation range of the workpiece is less likely to interfere with the wire guide, and the distance between the pair of wire guides can be made as narrow as possible. As a result, the holding force of the cutting wire can be maintained at a high level.

[0012] In the second invention, in the first invention, The control device sets the wire guide center O, which is the height between the centers of the pair of wire guides when viewed along the longitudinal direction of the wire guides, as the origin. P s Let O be the pivot center, r be the wire guide radius, and x be the distance from the wire guide center O to P. s The distance on the Z-axis from the cutting wire to P s Distance along the Z-axis to P, R0 is the center of the machining arc, A is the radius of the machining arc, and W is P. s When the distance from to R0 is the workpiece oscillation angle θ and C is the deviation between machining point 1 when the oscillation angle is 0 and machining point 2 when the oscillation angle is θ, a=xr W=Aa C=W(1-Cosθ) Therefore, if the reference position of the workpiece is P0, then the control position P of the workpiece, which is the target position when it is oscillated by θ, P=P0-C Control it so that it becomes like this.

[0013] According to the above configuration, by adjusting the contact position with the cutting wire due to oscillation so that the workpiece and wire are theoretically in point contact, the change in the deflection of the cutting wire is minimized, a uniform cutting force can be maintained, efficiency is further improved, and accuracy is stabilized.

[0014] In the third invention, in the first or the second invention, when the control device uses R as the working radius, the swing angle θ is θ m = Cos -1 ((W 2 + A 2 - R 2 ) / (2·A·W)) for the θ represented by m to perform control so as to be as follows.

[0015] According to the above configuration, the swing angle can be optimized so that the workpiece does not separate from the cutting wire, and cutting can be efficiently performed.

[0016] In the fourth invention, in the third invention, the swing angle θ, the machining arc A, and the workpiece radius R can be arbitrarily changed.

[0017] In the fifth invention, a swing mechanism for swingably supporting a workpiece, a lifting mechanism for supporting the swing mechanism so as to be movable up and down, a wire driving mechanism for rotating a pair of wire guides to move the cutting wire back and forth, prepare a wire saw device including a control device for controlling the swing mechanism, the lifting mechanism, and the wire driving mechanism, using the wire guide center O, which is the height between the pair of wire guides when viewed along the longitudinal direction of the wire guide, as the origin, P s as the swing center, r as the wire guide radius, x as the distance on the Z-axis from the wire guide center O to P s to P s as the distance on the Z-axis from the wire to P s to R0, θ as the swing angle of the workpiece, and C as the deviation amount between the machining point 1 when the swing angle is 0 and the machining point 2 when the swing angle is θ, a = x - r W = A - a C=W(1-Cosθ) And so, If the reference position of the workpiece is P0, then the control position P of the workpiece, which is the target position when it is oscillated by θ, P=P0-C The wire saw device is controlled in such a manner.

[0018] According to the above configuration, by adjusting the contact position with the cutting wire due to oscillation so that the workpiece and wire are theoretically in point contact, the change in the deflection of the cutting wire is minimized, a uniform cutting force can be maintained, efficiency is further improved, and accuracy is stabilized.

[0019] In the sixth invention, in the fifth invention, When R is the work radius, the oscillation angle θ is θ m = Cos -1 ((W 2 +A 2 -R 2 ) / (2·A·W)) θ represented by m The wire saw device is controlled in the following manner.

[0020] With the above configuration, the oscillation angle can be optimized to prevent the workpiece from separating from the cutting wire, allowing for efficient cutting.

[0021] In the seventh invention, the oscillation angle θ, machining arc A, and workpiece radius R can be arbitrarily changed in the fifth or sixth invention. [Effects of the Invention]

[0022] As described above, according to the present invention, in a wire saw device, it is possible to improve the cutting speed and reduce the wire breakage rate when the diameter of the workpiece is increased. [Brief explanation of the drawing]

[0023] [Figure 1] This is a perspective view showing a wire saw apparatus according to an embodiment of the present invention. [Figure 2] This is a block diagram of the control device and its surroundings. [Figure 3] This is a flowchart showing the control procedure for a wire saw device. [Figure 4] This is a schematic diagram illustrating the correlation between the wire and the pivot center. [Figure 5] This is an explanatory diagram showing the amount of machining point deviation C during oscillation. [Figure 6] This is an explanatory diagram showing the correlation between machining point 1 and machining point 2 during arc control. [Figure 7] This figure shows the oscillation angle θm at which the machining point coincides with the workpiece contour. [Figure 8A] This graph shows the changes in the table control variables in the simulation according to Example 1. [Figure 8B] This graph shows the change in table speed during the simulation according to Example 1. [Figure 9A] This graph shows the changes in the table control variables in the simulation according to Example 2. [Figure 9B] This graph shows the change in table speed during the simulation for Example 2. [Figure 10A] This graph shows the changes in the table control variables in the simulation according to Example 3. [Figure 10B] This graph shows the change in table speed during the simulation according to Example 3. [Figure 11A] This graph shows the changes in the table control variables in the simulation for Comparative Example 1. [Figure 11B] This graph shows the change in table speed during the simulation for Comparative Example 1. [Modes for carrying out the invention]

[0024] Embodiments of the present invention will be described below with reference to the drawings.

[0025] Figures 1 to 3 show a workpiece oscillating type wire saw apparatus 1 according to an embodiment of the present invention. This wire saw apparatus 1 is used to cut a workpiece (hereinafter referred to as "workpiece W"), such as a silicon ingot used in the manufacture of semiconductor devices or solar cells, into thin wafers at multiple locations simultaneously.

[0026] The wire saw device 1 is configured to cut a workpiece W by pressing it against a pair of parallel wire guides 2, 2, through which a cutting wire 3 is spirally wound, and then running the wire 3 along these guides.

[0027] Specifically, the wire saw device 1 has a device body 10 made of a metal frame or the like, and a lifting mechanism 4 is supported on the upper side of this device body 10. The lifting mechanism 4 includes, for example, a table 14 and a table drive motor 15 that raises and lowers the table 14. A swinging mechanism 30 that swings and supports the workpiece W is supported on this lifting mechanism 4 so as to be able to move up and down.

[0028] Although not shown in detail, the rocking mechanism 30 includes a power transmission unit, which for example comprises a rack and pinion and an arc-shaped guide. The workpiece rocking motor 31 rotates the pinion in the forward or reverse direction to drive the rack, causing the workpiece holder 32, which grips the workpiece W, to rock along the arc-shaped guide. The power transmission unit for this rocking mechanism 30 is not limited to such a rack and pinion structure, and may also be a ball screw, a belt (see Patent Document 2 or 3), etc.

[0029] Furthermore, cylindrical and prismatic workpieces W can be detachably attached to the workpiece holder 32.

[0030] Below the work holder 32, a wire drive mechanism 5 is provided that rotates a pair of cylindrical wire guides 2,2 to move the cutting wire 3, which is spirally wound around these wire guides 2,2 back and forth. The rotation axis of each wire guide 2,2 is connected to the output shaft of the corresponding wire guide drive motor 13, and the rotational drive of this wire guide drive motor 13 causes each wire guide 2,2 to rotate around its horizontal axis.

[0031] One end of the cutting wire 3 is located outside one of the wire guides 2 and extends to the wire supply device 6, guided by a plurality of disc-shaped pulleys P. The wire supply device 6 includes a supply-side bobbin 6a on which the new portion of the cutting wire 3 is wound, and an assist motor 6b that rotates the supply-side bobbin 6a, thereby feeding the cutting wire 3 to the wire guide 2. The other end of the cutting wire 3 is located outside the other wire guide 2 and extends to the wire winding device 7, guided by a plurality of disc-shaped pulleys P. The wire winding device 7 includes a winding-side bobbin 7a that winds the cutting wire 3 fed from the wire guide 2, and an assist motor 7b that rotates the winding-side bobbin 7a. In addition, a tension arm 11 is attached to one of the disc-shaped pulleys P located outside each wire guide 2 in order to control the tension of the cutting wire 3.

[0032] In the wire saw device 1 of this embodiment, the rotational drive of the wire guide drive motor 13 and the assist motors 6b and 7b alternately and repeatedly feeds out the cutting wire 3 and winds it back up by a predetermined length less than the feed length. As a result, the new portion of the cutting wire 3 is sequentially fed out from the wire supply device 6 side and sent to the wire winding device 7 side.

[0033] The wire saw device 1 has an operating unit 41 such as a touch panel, and various parameters are input via this operating unit 41 to operate the wire saw device 1.

[0034] The operation signals from the operation unit 41 are sent to the control device 20. The control device 20 is, for example, a microcomputer and includes a calculation unit 21, a storage unit 22, and a drive unit 23. Based on the results of calculations performed appropriately by the calculation unit 21, the assist motors 6b and 7b, the wire guide drive motor 13, the table drive motor 15, and the workpiece oscillating motor 31 are driven via the drive unit 23, and the driving status is displayed on a display unit 40 such as an LCD monitor.

[0035] -Arc control- First, in the wire saw device 1, as shown in Figure 1, a supply-side bobbin 6a on which a new portion of the cutting wire 3 is wound is installed, and the other end is attached to each component so as to be connected to the winding-side bobbin 7a.

[0036] Next, as shown in Figure 3, in step S01, the operating unit 41 is operated to turn on the power to the wire saw device 1, and the drive unit 23 issues instructions to drive the assist motors 6b and 7b, the wire guide drive motor 13, the table drive motor 15, the workpiece oscillating motor 31, etc., and the cutting wire 3 starts moving.

[0037] Next, in step S02, the workpiece oscillating motor 31 is driven to start oscillating the workpiece W.

[0038] Next, in step S03, the calculation unit 21 calculates the workpiece reference position P0 from P0 = V0 × t.

[0039] Next, in step S04, the calculation unit 21 calculates a table control amount C = (Aa)(1-Cosθ) corresponding to the workpiece oscillation angle θ. Specifically, as shown in Figure 4, the wire guide center O, which is the height between the pair of wire guides 2,2 when viewed along the longitudinal direction of the wire guides 2,2, is set as the origin.

[0040] And, as shown in Figure 5, P s Let O be the pivot center, r be the wire guide radius, and x be the distance from the wire guide center O to P. s Distance on the Z-axis from the wire to P sDistance along the Z-axis to P, R0 is the center of the machining arc, A is the radius of the machining arc, and W is P. s When the distance from to R0 is the workpiece oscillation angle θ and C is the deviation between machining point 1 when the oscillation angle is 0 and machining point 2 when the oscillation angle is θ, a=xr W=Aa C = W(1 - Cosθ) = (Aa)(1 - Cosθ) This is the result.

[0041] Next, in step S05, based on the calculated amount of the table control amount C, the workpiece position is moved by the table drive motor 15, workpiece oscillating motor 31, etc., at the instruction of the drive unit 23. In Figure 6, P s ' is P when the table position is P (up from P0 by C). s This shows that R0' represents the value of R0 when the table position is P (up by C from P0) and oscillated by θ.

[0042] Next, in step S06, it is determined whether the workpiece reference position P0 has reached the control position P (P=P0) of the workpiece W, which is the target for cutting completion. If it has not reached the target position, the process returns to step S03. If it has reached the target position, the process terminates.

[0043] - Miss prevention control - The oscillation angle θ is θ m By controlling it as follows, it is possible to prevent the cutting wire 3 from missing (a state in which the theoretical processing point moves outside the workpiece W). A typical example is θ in the case of a cylindrical workpiece (such as a silicon ingot). m The calculation is shown below.

[0044] As shown in Figure 7, the calculation unit 21 calculates θ(=θ) when the distance from the workpiece center W0 to the machining point 2 is equal to R. m The machining radius A is calculated as follows: Let h1 be the distance in the Z-axis direction from R0 to W0, and h2 be the distance in the Z-axis direction from W0 to the cutting wire 3. A = h1 + h2 And so, h1 and h2 are, h1 = W·Cosθ m h2=√(R 2 -(W·Sinθ m ) 2 ) It is represented as follows.

[0045] Substituting h1 and h2 into equation A, A = W·Cosθ m +√(R 2 -(W·Sinθ m ) 2 ) AW·Cosθ m =√(R 2 -(W·Sinθ m ) 2 ) (AW·Cosθ m ) 2 =R 2 -(W·Sinθ m ) 2 Sin 2 θ m = 1 - Cos 2 θ m Substitute this, (AW·Cosθ m ) 2 =R 2 -W 2 (1―Cos 2 θ m ) (AW·Cosθ m ) 2 =R 2 -W 2 +W 2 · Cos 2 θ m This is the result.

[0046] Expanding and simplifying, and then expanding the left side and the right side, A 2 -2·A·W·Cosθ m =R 2 -W 2 And so, cosθ m =((W 2 +A 2 -R 2 ) / (2·A·W)) Therefore θ m teeth, θ m = Cos -1 ((W 2 +A 2 -R 2 ) / (2·A·W)) It is represented as follows.

[0047] θ m It has two solutions, ± and θ. m The absolute value of is maximized when h² = 0.

[0048] -Circular arc control simulation- Next, the simulation results of arc control in the workpiece cutting method according to this embodiment will be described.

[0049] As a common condition, we assume that the table's operating speed can be 1500 mm / min.

[0050] The results for Examples 1-3 and Comparative Example 1 are shown in Figures 8A-11B, respectively.

[0051] In Example 1, the oscillation angle θ was set to 10 degrees, the oscillation angular speed to 1080 degrees / min, the ingot diameter (arc width) to 152 mm, and the machining arc radius A to 438 mm.

[0052] As shown in Figure 8A, by changing the table control amount C at the start and end of the cut, it was found that stable arc control can be performed within the range of operable table speeds shown in Figure 8B.

[0053] In Example 2, the oscillation angular velocity was slowed to 800 deg / min compared to Example 1, while all other conditions remained the same.

[0054] As shown in Figure 9A, the table control amount C at the start and end of cutting changed more gradually in the horizontal direction than in Example 1. It was also found that stable arc control could be performed within the operating range for the table speed shown in Figure 9B.

[0055] In Example 3, the ingot diameter (arc width) was increased to 340 compared to Example 1. On the other hand, the oscillation angular speed was significantly slowed down to 400 deg / min, and the machining arc radius A was set to 964 mm, while all other conditions remained the same.

[0056] As shown in Figure 10A, the table control amount C at the start and end of cutting expanded significantly in the horizontal direction compared to Example 1, while the table control amount itself increased. This allowed for stable arc control within the operating range of the table speed shown in Figure 10B.

[0057] In Comparative Example 1, the oscillation angular velocity was increased to 1080 deg / min compared to Example 3, while all other conditions remained the same.

[0058] As shown in Figure 11A, the table control amount C at the start and end of cutting is larger than in Examples 1-3, and the table speed shown in Figure 10B exceeds the operating range. However, if the operating range of this table speed is expanded, cutting of the workpiece W by arc control is possible even in Comparative Example 1.

[0059] As can be seen from Comparative Example 1 and Example 3, to cut a workpiece W with a relatively large diameter ingot of 340 mm, it is desirable to increase the table control amount to about 17.5 mm and slow the oscillation angular speed to 400 deg / min. However, as mentioned above, it is also possible to increase the oscillation angular speed by expanding the range of table speed operation.

[0060] Therefore, according to the wire saw device 1 of this embodiment, it is possible to improve the cutting speed and reduce the wire breakage rate when working with larger diameter workpieces.

[0061] (Other embodiments) The present invention may also have the following configuration in the above embodiment.

[0062] In other words, in the above embodiment, a microcomputer was described as an example of a control device (controller). However, the control device controls the "wire saw device 1" and can be physically configured in any way as long as it has a CPU (processor) and memory. For example, the control device may utilize software (programs), such as a microcomputer or a programmable logic controller (PLC). Alternatively, the control device unit may be realized by combining hardware (circuit components).

[0063] The wire saw device 1 to which the present invention can be applied is not limited to the wire saw device 1 described in the above embodiment, but is broadly applicable to any wire saw device 1 of the type that performs cutting by pressing the workpiece against the cutting wire 3 while simultaneously oscillating the workpiece as it is run along a cutting wire 3 that is spirally wound around a plurality of wire guides. For example, the present invention can also be applied to discharge-type wire saw devices.

[0064] Furthermore, the shape of the workpiece W to which the present invention can be applied (shape before processing) is not particularly limited, and the present invention can be broadly applied to workpieces W having various shapes such as cylindrical or rectangular parallelepipeds. In the case of a non-circular workpiece W, for example a square workpiece W, the range of movement of the contact point due to oscillation differs from that of a circular workpiece at the start and end of cutting. In this case, the point contact can be kept within the range of movement by fixing or changing the processing arc.

[0065] Furthermore, the material of the workpiece W to which the present invention can be applied is not particularly limited to silicon, but when the workpiece W is made of a difficult-to-machine material such as sapphire or silicon carbide (SiC), it is preferable to use a fixed abrasive wire as the cutting wire 3. When using a fixed abrasive wire as the cutting wire 3, the cutting process may be performed while supplying cooling water or the like instead of a slurry containing abrasive grains.

[0066] The embodiments described above are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses. [Explanation of symbols]

[0067] 1. Wire saw device 2 Wire guides 3. Cutting wire 4. Lifting mechanism 5. Wire drive mechanism 6. Wire feeding device 6a Supply side bobbin 6b Assist motor 7 Wire winding device 7a Winding side bobbin 7b Assist motor 10 Main unit of the device 11 Tension Arm 13 Wire guide drive motor 14 tables 15 Table drive motor 20 Control device 21 Arithmetic section 22 Memory section 23 Drive unit 30. Oscillating mechanism 31 Workpiece Oscillating Motor 32 Work Holders 40 Display section 41 Operation section P Pulley Double job

Claims

1. A rocking mechanism that supports the workpiece in a rocking manner, A lifting mechanism that supports the aforementioned rocking mechanism so that it can move up and down, A wire drive mechanism that rotates a pair of wire guides to move the cutting wire back and forth, The system includes a control device for controlling the rocking mechanism, the lifting mechanism, and the wire drive mechanism, The control device controls the workpiece to oscillate using the oscillating mechanism while maintaining the oscillating center of the workpiece at or near the center of the cross-sectional shape of the workpiece, so that the workpiece and the cutting wire always come into contact at one point on the arc of the workpiece. The wire guide center O, which is the height between the centers of the pair of wire guides when viewed along the longitudinal direction of the wire guides, is taken as the origin. When Ps is the pivot center, r is the wire guide radius, x is the distance on the Z-axis from the wire guide center O to Ps, a is the distance on the Z-axis from the cutting wire to Ps, R0 is the center of the machining arc, A is the machining arc radius, W is the distance from Ps to R0, θ is the workpiece pivot angle, and C is the deviation between machining point 1 when the pivot angle is 0 and machining point 2 when the pivot angle is θ, a = x - r W = A - a C=W(1-Cosθ) Therefore, if the reference position of the workpiece is P0, then the control position P of the workpiece, which is the target position when it is oscillated by θ, P = P₀ - C Control it so that it becomes like this. A wire saw device characterized by the following features.

2. When R is the workpiece radius, the control device's oscillation angle θ is expressed by the following formula: ｍ Control it so that it is as follows: i ｍ =Cos －１ ((W) ２ +A ２ -R ２ ) / (2・A・W)) The wire saw device according to feature 1.

3. The oscillation angle θ, machining arc A, and workpiece radius R can be arbitrarily changed. The wire saw device according to feature 2.

4. A rocking mechanism that supports the workpiece in a rocking manner, A lifting mechanism that supports the aforementioned rocking mechanism so that it can move up and down, A wire drive mechanism that rotates a pair of wire guides to move the cutting wire back and forth, A wire saw device is prepared, which includes a control device for controlling the rocking mechanism, the lifting mechanism, and the wire drive mechanism. The wire guide center O, which is the height between the pair of wire guides when viewed along the longitudinal direction of the wire guides, is taken as the origin. P ｓ as the swing center, r as the wire guide radius, x as the distance on the Z-axis from the wire guide center O to P ｓ to the distance on the Z-axis from the wire to P ｓ to the distance on the Z-axis from the wire to P, R ０ as the center of the machining arc, A as the machining arc radius, W as the distance from P ｓ to R ０ to the distance to R, θ as the swing angle of the workpiece, C as the deviation amount between the machining point 1 when the swing angle is 0 and the machining point 2 when the swing angle is θ a = x - r W = A - a C=W(1-Cosθ) And so, The reference position of the workpiece is P ０ Therefore, the control position P of the workpiece, which is the target position when it is oscillated by θ, P=P ０ -C Control the wire saw device so that it becomes A method for cutting a workpiece, characterized by the features described above.

5. When R is the work radius, the oscillation angle θ is expressed by the following equation: ｍ The wire saw device is controlled as follows: i ｍ =Cos －１ ((W) ２ +A ２ -R ２ ) / (2・A・W)) The method for cutting a workpiece as described in feature 4.

6. The oscillation angle θ, machining arc A, and workpiece radius R can be arbitrarily changed. The method for cutting a workpiece according to claim 4 or 5.

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