Method for cutting a plurality of slices from a workpiece by means of a wire saw during a series of cutting operations

Abstract

The invention relates to a method for cutting a plurality of slices from a workpiece (4) by means of a wire saw, wherein a wire array (2) is tensioned in a plane between two wire guide rollers (1), wherein each of the two wire guide rollers (1) comprises at least one chamber (18) and a housing portion (8), which surrounds a core portion (17) of the wire guide roller (1) and is configured with a guide groove for a wire section. The method comprises conveying the workpiece (4) via the wire array (2), at the same time changing the length of the housing portions (8) of the two wire guide rollers (1) by controlling the temperature of the chambers (18) of the wire guide rollers (1) with a first cooling fluid according to a specification of a first temperature profile, and at the same time moving the workpiece (4) along a workpiece axis according to a specification of a second correction profile.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for cutting out a plurality of slices from a workpiece during a series of parting (dicing) operations by means of a wire saw, wherein the wire saw comprises a wire array consisting of moving wire sections of a sawing wire and an actuating device, and the wire array is tensioned in a plane between two wire guide rollers, and wherein each of the two wire guide rollers is supported between a fixed bearing and a floating bearing and comprises at least one chamber and a housing part, which encloses a core part of the wire guide roller and is configured with a guide groove for the wire sections. During each of the parting operations, in the presence of a hard material and a working fluid that act abrasively on the workpiece, a respective workpiece is fed through the wire array by means of the actuating device along a feed direction that is perpendicular to the workpiece axis and to the plane of the wire array. BACKGROUND

[0002] This method for cutting out a plurality of slices can be implemented by means of a kiss-cutting slice or a grinding slice.

[0003] In the case of a kiss-cutting slice, a working fluid in the form of a slurry consisting of a hard material in a liquid carrier medium is fed to a working space formed between the wire surface and the workpiece. In the case of a kiss-cutting slice, the material is removed by means of a three-body interaction involving the tool carrier (sawing wire), the tool (abrasive) and the workpiece.

[0004] In the case of a grinding slice, a sawing wire with a hard material firmly bonded in its surface is used, and a working fluid is supplied, which itself contains no grinding material and serves as a cooling lubricant. In the case of a grinding slice, the material is removed by means of a two-body interaction involving the diamond-coated sawing wire as a tool and the workpiece.

[0005] In the case of a conventional wire saw, each of the wire guide rollers is provided near each of its end faces with a bearing that is connected in a fixed manner to the machine frame and is referred to as a fixed bearing, and near the opposite end face with a bearing that is movable relative to the machine frame in the axial direction of the wire guide roller and is referred to as a floating bearing.

[0006] The wire guide rollers of the wire array usually comprise a core part made of metal, which is usually surrounded (clad) by a housing part made of, for example, polyurethane. The housing part has a plurality of grooves for guiding the sawing wire of the wire array forming the wire saw. The housing part is usually fastened to the core part of the respective wire guide roller of the wire array so that it can expand or contract axially unhindered at both ends when there are temperature changes. Nevertheless, the housing part can be fixed to one or both sides of the wire guide roller respectively by one or two clamping rings.

[0007] There are known measures which aim to counteract changes in the arrangement of the wire array and the workpiece relative to each other during the cutting-off operation in order to improve the planar parallelism of the main surface of the slice to be cut off.

[0008] US 2002 / 0 174 861 A1 describes a method which envisages controlling the temperature of the workpiece in order to limit the warping of the slice to be cut off.

[0009] In US 2015 / 0 158 203 A1 it is proposed to selectively cause a length change of the housing portion by a temperature change in the core portion of the wire guide roller in order to improve the flatness of the cut-off slice.

[0010] US 2012 / 0 240 915 A1 describes a method which provides for independent cooling of the wire guide roller and its fixed bearings in order to reduce the relative axial movement of the wire section and the workpiece caused by temperature changes.

[0011] US 5 377 568 discloses a method in which the position of a reference surface located on the outside of the wire guide roller relative to the machine frame is measured and a thermal length increase or length decrease of the wire guide roller is achieved by adjusting the temperature inside the wire guide roller until the measured position change of the reference surface has been compensated for again.

[0012] WO 2013 / 079683 A1 discloses a method in which firstly the slice shapes obtained at different temperatures of the wire guide roller bearings are measured and each of these shapes is stored together with the corresponding associated bearing temperature, and then in a subsequent cut, the bearing temperature is selected which best matches the desired target shape.

[0013] US 5 875 770 discloses a method in which the shape of a slice from a cut is measured, a correction curve in relation to the cutting depth is calculated by forming a difference relative to a desired ideal shape of the slice, and in a subsequent cut the workpiece is moved relative to the wire array in the axial direction during the cutting-off operation in accordance with the correction curve.

[0014] Despite these measures, there is still a need for improvement, on the one hand because these measures only have a limited effect and on the other hand because the requirements for the flatness and planar parallelism of the slice are increasing, in particular in the semiconductor industry. SUMMARY

[0015] It is an object of the present application to produce a usable slice whose shape matches the target shape as closely as possible.

[0016] The object of the present invention is achieved by a method for cutting out a plurality of slices from a workpiece by means of a wire saw during a series of cutting-off operations divided into an initial cut and subsequent cuts, wherein the wire saw comprises a wire array consisting of moving wire segments of a sawing wire and an actuating device, and the wire array is tensioned in a plane between two wire guide rollers, wherein each of the two wire guide rollers is supported between a fixed bearing and a floating bearing and comprises at least one chamber and a housing portion, which encloses a core portion of the wire guide roller and is configured with a guide groove for the wire segments, the method comprising

[0017] During each of the cutting-off operations, in the presence of hard material and working fluid acting abrasively on the workpiece, a respective workpiece is fed through the wire array along a feed direction perpendicular to the workpiece axis and to the plane of the wire array by means of the actuating device, which comprises

[0018] During each of the cutting-off operations, while the workpiece is fed through the wire array, the length of the housing portions of the two wire guide rollers is simultaneously changed by regulating the temperature of the chambers of the wire guide rollers with a first cooling fluid according to the specification of a first temperature profile, which specifies the temperature of the first cooling fluid as a function of the cutting depth and is related to a first correction profile, which specifies the length variation of the housing portions as a function of the cutting depth;

[0019] During each of the cutting-off operations, while the workpiece is fed through the wire array, the workpiece is simultaneously moved along the workpiece axis by means of the actuating elements according to the specification of a second correction profile, which specifies the travel of the workpiece, wherein the first correction profile and the second correction profile counteract (suppress) a shape deviation; and

[0020] The shape deviation is determined before each of the cutting-off operations.

[0021] The method can be configured to cut lap slices or ground slices. The cutting depth (doc) represents the length opposite to the feed direction in the area from the entry into the workpiece cut to the exit from the workpiece cut.

[0022] For example, the changing of the axial length of the housing part and the line guide roller in the line guide roller that tensions the line array by adjusting the temperature of the chamber of the line guide roller can be implemented in the manner proposed in US 2015 / 0 158 203 A1 (hereinafter referred to as line guide heat control, WGHC). Furthermore, a first cooling fluid is passed through the chamber of the respective line guide roller according to the specification of a first temperature profile, wherein the temperature of the chamber of the line guide roller is adjusted with the first cooling fluid, the first temperature profile specifying a temperature of the first cooling fluid that is dependent (depends) on the cutting depth. The first temperature profile is related to a first correction profile that specifies a length change of the respective housing part of the line guide roller dependent on the cutting depth. In advance, the temperature change of the first coolant required to cause the specified length change of the housing part of the respective line guide roller is determined experimentally. The first correction profile is contrary to the shape deviation determined before each of the cutting operations.

[0023] More than one chamber can be provided in the core part of the line guide roller, and a cooling fluid is supplied to each chamber independently, in any case the temperature of each chamber following its own temperature profile. In this case, these temperature profiles jointly cause the length change of the housing part of the respective line guide roller required by the first correction profile.

[0024] The simultaneous movement of the workpiece along the workpiece axis during each cutting operation while feeding the workpiece through the line array according to the specification of a second correction profile by means of an actuating element (hereinafter referred to as IPC, ingot positioning control) is employed together with WGHC. The actuating element is preferably a piezoelectric actuator. The second correction profile is likewise contrary to the shape deviation determined before each cutting operation.

[0025] The length change of the housing part of the line guide roller dependent on the cutting depth and the movement of the workpiece along its longitudinal axis (workpiece axis) dependent on the cutting depth that is implemented by means of WGHC takes place relative to a common reference system (for example the machine frame) and thus relative to the line guide roller or the line array.

[0026] The first correction profile and the second correction profile together form a total correction profile that minimizes the shape deviation.

[0027] The adjustment of the temperature of the fixed bearing (hereinafter referred to as WGTC, line guide temperature control) leads to a change in the position of the line guide roller and thus of the line array relative to the position of the workpiece (rod, ingot), since this leads to a movement of the floating bearing and the line guide roller relative to the common reference system in the direction of the rotational axis of the line guide roller.

[0028] According to a preferred embodiment of the invention, WGHC and IPC are combined with WGTC. In this case, the total correction curve includes a third correction curve dependent on the cut depth, i.e., a curve specifying the travel of the floating bearing achieved by means of WGTC and therefore the travel of the line-guided bearing of the linear array.

[0029] There are specific advantages associated with using WGHC and IPC, or a combination of WGHC, IPC, and WGTC. When WGHC and IPC, or WGHC, IPC, and WGTC, are used in combination, a larger range of motion (stroke) of the line guide roller relative to the workpiece can be obtained compared to the range achievable with only one of these measures. The range of linear correlation between the motion of the floating bearing and the variable causing the motion is wider than the corresponding range achievable with only one of these measures. Compared to the case of IPC, the response time from changing the variable causing the motion to the actual occurrence of the motion is significantly longer with WGHC or WGHC and WGTC, especially if the actuating element is a piezoelectric actuator. WGHC and WGTC measures on the one hand, and IPC measures on the other, thus have different control bandwidths. Therefore, it is advantageous to use IPC to counteract relatively high-frequency shape deviations (i.e., shape deviations that change with relatively large gradients depending on the cutting depth) and WGHC or WGHC and WGTC to counteract relatively low-frequency shape deviations.

[0030] As an embodiment, the present invention preferably includes a method using a first temperature profile that depends on the cutting depth to specify the temperature of a first cooling fluid and is associated with a first correction profile that depends on the cutting depth to specify the length variation (WGHC) of the outer shell portion of the line guide roller; the method using a second correction profile that specifies the workpiece travel (IPC); and the method using a second temperature profile that depends on the cutting depth to specify the temperature of a second cooling fluid and is associated with a third correction profile that specifies the movement of the floating bearing of the line guide roller and thereby the movement of the line guide roller itself in the direction of its rotation axis (WGTC).

[0031] The temperature of the line guide roller is adjusted by means of WGHC (length variation of the line guide roller and the length variation of the outer shell of the line guide roller), the temperature of the fixed bearing is adjusted by means of WGTC (axial position variation of the line guide roller), and the relative movement of the workpiece and the line guide roller is caused by means of IPC (moving the workpiece). The relative movement of the individual line segments of the line array relative to the workpiece is achieved by means of the length variation of the line guide roller (WGHC). Therefore, there are specific advantages associated with this embodiment. Deviations in the shape of the slices obtained by the cutting operation from the ideal shape are largely compensated for. These deviations vary for different positions of the slices in the workpiece, and thus require different movements of the relative positions of the line segments and the workpiece according to the positional requirements, ensuring that all slices are as close as possible to the ideal shape.

[0032] Shape deviation is determined before the cutting operation and refers to the deviation of the shape curve of the slice or the average shape curve of the slice from the reference shape curve.

[0033] The determination of shape deviation is preferably based on a comparison of the average shape curve of the cut slices with a reference shape curve. This comparison provides a total correction curve that, even before the cutting operation, determines the length variation of the line guide roller housing (by means of WGHC), the workpiece stroke (by means of IPC), and, where applicable, the stroke of the line guide roller (by means of WGTC), which depend on the cutting depth (as a function of the cutting depth) and are required to avoid shape deviations that would be expected without these countermeasures. The total correction curve is divided into a first correction curve, a second correction curve, and, where applicable, a third correction curve, and this determines the proportion of length variation or stroke to be performed by means of WGHC and IPC, and, where applicable, by means of WGTC. This proportion may be divided equally or differently.

[0034] The surface of the slice consists of a main surface and edge surfaces. The main surface includes the front and back sides of the slice. As is common in warp measurements, the slice can be measured by being arranged between a pair of sensors. Each of the sensors measures the distance of the slice's facing side to the main surface at a measurement point. The measurement points can be distributed on the main surface or located along the diameter of the slice. The measurement points are preferably located at position i along the diameter of the slice (specifically opposite to the feed direction), and thus each measurement point is associated with a specific cutting depth. The density of the measurement points is preferably not less than one per centimeter, and the distance between a measurement point and its nearest neighbor is preferably the same for all measurement points.

[0035] The shape curve of the slice is a line connecting measurement points si, which are calculated at position i according to the rule si = 1 / 2[D - (FDi - BDi)], where D is the distance between the sensors, FDi is the distance between the upper sensor and the corresponding measurement point on the front side of the slice, and BDi is the distance between the lower sensor and the corresponding measurement point on the rear side of the slice. It should be noted that the invention can also be implemented using an alternative definition of the shape curve, provided that the alternative definition encodes the shape of the slice as a function of the slice depth.

[0036] The average shape curve of a slice is obtained by averaging the shape curves of multiple slices. The reference shape curve is the desired (ideal) shape curve, preferably the shape curve of a slice with perfectly flat and mutually parallel main surfaces. The average shape curve is determined for slices produced by preferably 1 to 5 cutting operations performed using the same wire saw, wherein these cutting operations are performed immediately adjacent to the cutting operation to be performed by that wire saw. The selection of slices for creating the average shape curve can be based on slices or on cutting, or may include both. In the case of slice-based selection, certain slices from a cutting operation are used to determine the corresponding average shape curve by averaging, while other slices are excluded. For example, only those slices with specific positions in the workpiece are considered in the averaging process, such as only every 15th to 25th slices along the workpiece axis. Another possibility for slice-based selection is to exclude slices with the largest and smallest shape curve deviations relative to the average shape curve of all slices in the cutting operation (the so-called truncated mean). Alternatively, slices whose shape curves deviate from the average shape curve of all slices from the cutting operation by more than 1 to 2σ (sigma) can be excluded from the averaged slices. In the cut-based selection, all slices from at least one cutting operation are used to determine the average shape curve, and all slices from at least one other cutting operation are excluded.

[0037] The average shape profile of the cut slice changes during a series of cutting operations. These changes are preferably used to evaluate the performance of the wire saw. They can indicate wear on the casing of the saw wire and / or the wire guide roller, or on some other component of the wire saw that is subject to wear. Therefore, preferably, a threshold for shape deviation is defined, and when this threshold is reached or exceeded, maintenance activities (predictive maintenance activities) are initiated instead of another cutting operation. Even before this threshold is reached, such changes can be used as justification for taking regulatory measures to counteract the deterioration of work results due to wear. For example, such regulatory measures could be changing the composition and / or temperature of the working fluid and / or changing the saw wire speed and / or other process-specific parameters.

[0038] Cutting operations performed after changes have occurred in the saw system represent specific circumstances. Such changes occur in the saw system when there are changes in the wire guide rollers, mechanical adjustments to the wire saw, or changes in the physical or chemical properties of the working fluid. The first or initial cutting operations after a change in the saw system (i.e., the so-called initial cut) preferably consist of 1 to 5 cutting operations. For the initial cut, shape deviations are preferably determined by comparing the average shape curve of the cut with a reference shape curve, wherein the average shape curve of the cut produced by the same wire saw during one or more initial cuts performed before the saw system was changed is used.

[0039] Furthermore, preferably, workpiece temperature control (spool cooling, IC) is provided in place of WGTC or as a fourth measure in addition to WGHC, IPC, and WGTC during each of the cutting operations. More specifically, this control is achieved by wetting the workpiece with a cooling medium via a closed control loop, wherein the workpiece temperature forms a controlled variable, and the temperature of the cooling medium forms a manipulated variable of the control loop. The reference variable of the control loop is preferably a constant temperature. The cooling medium is preferably a fluid or a working fluid used in overlapping or grinding cutters. By controlling the workpiece temperature, shape deviations of the cutter caused by thermal expansion of the workpiece can be additionally limited. The control loop can be implemented, for example, as described in US 2002 / 0 174861A1.

[0040] The wire saw used according to the invention comprises two or more wire guide rollers, such as three or four. Temperature regulation of the chambers and fixed bearings of the wire guide rollers can be limited to two of the wire guide rollers, wherein the wire array is tensioned between the two wire guide rollers, and the workpiece is fed (infeeded) by means of the two wire guide rollers.

[0041] The workpiece is preferably made of a semiconductor material such as silicon in a polycrystalline or monocrystalline state. The perimeter of the workpiece's cross-section is square, rectangular, or circular. In the case of a cylindrical workpiece, the workpiece axis extends through the center of the cylinder. The method according to the invention is particularly suitable for producing circular semiconductor wafers made of monocrystalline silicon with a diameter of at least 200 mm, and especially at least 300 mm.

[0042] The details of the present invention will now be described with reference to the accompanying drawings. Attached Figure Description

[0043] Figure 1 The features of a wire saw that functions in the use of the present invention are illustrated schematically.

[0044] Figure 2 Details of these features are shown.

[0045] Figure 3Further details of these features are shown.

[0046] Figure 4 The arrangement of the slices between two sensors used to determine the shape deviation of the slices prior to the cutting operation is shown.

[0047] Figure 5 Details of features related to preferred exemplary embodiments using WGHC and WGTC are shown.

[0048] Figure 6 Details of features related to another preferred exemplary embodiment using WGHC and WGTC are shown.

[0049] List of reference numerals used

[0050] 1. Line guide roller (lead roller)

[0051] 2-line array

[0052] 3. Saw wire

[0053] 4. Workpiece

[0054] 5. Fixed bearings

[0055] 6 Floating Bearings

[0056] 7 racks

[0057] 8. Outer shell

[0058] 9. Space for internal temperature regulation of the fixed bearing in WGTC

[0059] 9a Space for external temperature regulation of stationary bearings in WGTC

[0060] 10 Directional arrows

[0061] 11 Directional arrows

[0062] 12 Actuation device

[0063] 13 Control unit for WGHC

[0064] 14 Data Processing Unit

[0065] 15 Control unit for IPC

[0066] 16 Control Units for WGTC

[0067] 17 Core Section

[0068] 18 chambers

[0069] 19 Upper Sensor

[0070] 20 Lower Sensors

[0071] 21 slices

[0072] 22. Device for regulating workpiece temperature

[0073] 23. Axis of rotation

[0074] 24 bolts

[0075] 25. Flow direction

[0076] 26 directional arrows Detailed Implementation

[0077] Figure 1 Features of a wire saw suitable for implementing the method according to the invention are shown. The wire saw comprises a wire array 2 consisting of moving wire segments of saw wire 3, the wire array 2 being tensioned in a plane between two wire guide rollers 1. During the cutting operation, a workpiece 4 is fed through the wire array 2 by means of an actuation device 12 in a supply direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array 2. During this operation, the length of the wire guide roller 1 tensioning the wire array 2 (and therefore the length of its housing 8) is changed according to a first correction curve in a direction corresponding to direction arrow 10, and the workpiece 4 moves according to a second correction curve in a direction corresponding to the workpiece axis of direction arrow 11. Furthermore, the floating bearing 6 of the corresponding wire guide roller (and the corresponding wire guide roller itself) can simultaneously move according to a third correction curve in a direction corresponding to direction arrow 10, and / or the temperature of the workpiece 4 can be controlled by wetting the workpiece 4 with a cooling medium via a closed control loop, wherein the temperature of the workpiece 4 forms a controlled variable, and the temperature of the cooling medium forms a manipulated variable of the control loop. The first correction curve, the second correction curve, and, where applicable, the third correction curve, are opposite to (suppress) the shape deviation determined before each of the cutting operations. The first correction curve, the second correction curve, and, where applicable, the third correction curve are stored in the data processing unit 14. The first and second control units 13, 15 for implementing WGHC and IPC, and the third control unit 16 for implementing WGTC where applicable, control the heat exchanger for regulating the temperature of the chamber and the actuating element for moving the workpiece 4, and, where applicable, control the heat exchanger for regulating the temperature of the fixed bearing of the wire guide roller. If ingot cooling (IC) is envisioned, the wire saw also includes a device 22 for regulating the temperature of the workpiece 4. By means of this device 22, during each of the cutting operations, the workpiece 4 is fed through the wire array 2, while the temperature of the workpiece 4 is controlled by wetting the workpiece 4 with a cooling medium via a closed control loop, wherein the temperature of the workpiece 4 forms a controlled variable, and the temperature of the cooling medium forms a manipulated variable of the control loop.

[0078] like Figure 2 As shown, the wire guide roller 1 is mounted between a fixed bearing 5 and a floating bearing 6. The fixed bearing 5 and the floating bearing 6 are supported on a frame 7. The core portion 17 of the wire guide roller 1 is surrounded by a housing portion 8, which has a groove in which the saw wire 3 travels. The fixed bearing 5 includes a space 9 for internal temperature regulation and / or a space 9a for external temperature regulation. A second cooling fluid passes through spaces 9 and 9a to regulate the temperature of the fixed bearing 5. If the temperature of the second cooling fluid is increased, the thermal expansion of the fixed bearing 5 causes the wire guide roller 1 to move axially in the direction of the floating bearing 6, and the floating bearing 6 moves outward relative to the frame 7 in the direction indicated by arrow 10. If the temperature of the second cooling fluid is decreased, it causes the wire guide roller 1 and the floating bearing 6 to move in the opposite direction. The temperature of the second cooling fluid is specified by a second temperature profile dependent on the cutting depth, which is correlated with a third correction profile. A control unit 16 connected to the heat exchanger and pump ensures that the second cooling fluid passing through the fixed bearing 5 has the temperature specified by the second temperature profile at a certain cutting depth. The data processing unit 14 transmits a second temperature curve to the control unit 16, which causes the floating bearing to move according to the specifications of a third correction curve.

[0079] Figure 3 Two cavities in the core portion 17 of the line guide roller are shown, forming two chambers 18. A first cooling fluid flows through the two chambers 18 to regulate the temperature of the chambers 18, thereby changing the length of the outer shell portion 8 of the corresponding line guide roller in the direction corresponding to the directional arrow 10 according to the specifications (technical parameters or content) of the first correction curve. Bolts 24 coaxially connect the fixed bearing 5 and the floating bearing 6.

[0080] Figure 4 The arrangement of a slice 21 between two sensors 19 and 20 for determining shape deviation prior to the cutting operation is shown. Sensors 19 and 20 measure the distance FDi between the front side of sensor 19 and the front side of slice 21, and the distance BDi between the rear side of sensor 20 and the rear side of slice 21, at a specific position i along the diameter of slice 21 in the feed direction, according to a given cutting depth. The slice shape curve is a line connecting the measured values ​​si calculated according to the rule si = 1 / 2[D - (FDi – BDi)], where D represents the distance between the sensors. The slice shape deviation is obtained by comparing the slice shape curve with a reference shape curve. The deviation relative to the reference shape curve, depending on the cutting depth, corresponds to a total correction curve, which is divided between WGHC and IPC, and, where applicable, WGTC, in the form of a first correction curve, a second correction curve, and, where applicable, a third correction curve.

[0081] Figure 5 Details of the features of a preferred exemplary embodiment using WGHC and WGTC are shown.

[0082] The control unit 13 for WGHC (length variation of the outer shell portion 8 of the line guide roller 1 in a direction 10 parallel to its axis of rotation 23) regulates the temperature of the first cooling fluid, which, after being distributed in parallel, first passes through the chamber 18 spanning the two upper line guide rollers of the line array. The first cooling fluid is then recombined and returned to the control unit 13.

[0083] The control unit 16 for WGTC (movement of the line guide roller 1 in direction 26 parallel to its axis of rotation 23) regulates the temperature of the second cooling fluid, which, after being distributed in parallel, first passes through the internal temperature regulation space 9 of the fixed bearing 5 for the two upper line guide rollers spanning the line array. Then, the second cooling fluid is used to regulate the temperature of the two lower line guide rollers before they are recombined and return to the control unit 16. Temperature regulation of the lower line guide rollers is not absolutely necessary, but rather to dissipate frictional heat generated here, for example, as a result of bearing friction during the rotation of the line guide rollers. The flow directions of the first and second cooling fluids are indicated by arrow 25. The first and second cooling fluids are supplied to and discharged from the rotating line guide rollers via a rotating fluid supply passage. A coaxial dual rotating supply passage is used.

[0084] exist Figure 5 In the exemplary embodiment shown, WGTC is therefore performed by means of internal cooling within the fixed bearing and the supply and discharge of a second cooling fluid via a coaxial dual-rotation supply passage. The second cooling fluid is supplied in and out (input and output) via a rotational supply passage mounted on the fixed bearing side, while the first cooling fluid is supplied in and out via a rotational supply passage mounted on the floating bearing side. The temperature regulation circuit for WGTC passes through the upper and lower guide rollers, while the temperature regulation circuit for WGHC passes only through the upper guide roller.

[0085] Figure 6 Details of features of another preferred exemplary embodiment using WGHC and WGTC are shown.

[0086] The control unit 13 for WGHC (length variation of the outer shell portion 8 of the line guide roller 1 in a direction 10 parallel to its axis of rotation 23) regulates the temperature of a first cooling fluid, which, after being distributed in parallel, first passes through chambers 18 spanning the two upper line guide rollers of the line array. The first cooling fluid is then used to regulate the temperature of the two lower line guide rollers before they are recombined and return to the control unit 13.

[0087] The control unit 16 for WGTC (movement of line guide roller 1 in a direction 26 parallel to its axis of rotation 23) regulates the temperature of the second cooling fluid, which, after being split in parallel, first passes through an external temperature regulation space 9a for the fixed bearing 5 across the two upper line guide rollers of the line array, and is then used to regulate the temperature of the two lower line guide rollers before they are recombined and return to the control unit 16.

[0088] Therefore, in Figure 6 In the exemplary embodiment shown, WGTC is performed using external temperature regulation via a fixed bearing. A first cooling fluid for WGTC is supplied and discharged via a dual-rotation supply passage mounted on the fixed bearing side. Similar to the temperature regulation of the lower guide roller, the supply and discharge of a second cooling fluid for WGTC is implemented at the non-rotating external fixed bearing bushing via a fixed supply passage.

[0089] The above description of the illustrative embodiments should be understood as exemplary. This disclosure enables those skilled in the art to understand the invention and its associated advantages, while also including variations (changes) and modifications to the described structures and methods that are readily apparent to those skilled in the art.

Claims

1. A method for cutting out a plurality of slices from a workpiece by means of a wire saw during a series of dicing operations divided into an initial cut and subsequent cuts, wherein, The wire saw comprises a wire array consisting of moving wire segments of a sawing wire and an actuating device, and the wire array is tensioned in a plane between two wire guide rollers, wherein each of the two wire guide rollers is supported between a fixed bearing and a floating bearing and comprises at least one chamber and a housing portion surrounding a core portion of the wire guide roller and being configured with a guiding groove for the wire segments, the method comprising During each of the cutting-off operations, in the presence of hard material and working fluid abrasively acting on the workpiece, the respective workpiece is fed through the wire array along a feed direction perpendicular to a workpiece axis and perpendicular to the plane of the wire array by means of the actuating device, which comprises During each of the cutting-off operations, while feeding the workpiece through the wire array, the length of the housing portions of the two wire guide rollers is simultaneously changed by regulating the temperature of the chambers of the wire guide rollers with a first cooling fluid according to a specification of a first temperature profile, which specifies the temperature of the first cooling fluid in dependence on the cutting depth and in correlation with a first correction profile, which specifies the length change of the housing portions in dependence on the cutting depth; During each of the cutting-off operations, while feeding the workpiece through the wire array, the workpiece is simultaneously moved along the workpiece axis by means of actuating elements according to a specification of a second correction profile, which specifies the travel of the workpiece, wherein the first correction profile and the second correction profile inhibit a shape deviation; and The shape deviation is determined before each of the cutting-off operations by comparing an average shape profile of cut-off slices with a reference shape profile.

2. The method of claim 1, wherein, The average shape profile is determined by averaging shape profiles of selected slices, wherein the selection is based on slices, based on cuts, or based on slices and based on cuts.

3. The method of claim 1 or 2, wherein, The cut-off slices originate from at least 1 to 5 cutting-off operations immediately preceding the respective cutting-off operation.

4. The method of any of claims 1 to 2, wherein, The method comprises, during each of the cutting-off operations, feeding the workpiece through the wire array while simultaneously axially moving the floating bearings of the two wire guide rollers by regulating the temperature of the fixed bearings of the wire guide rollers with a second cooling fluid according to a specification of a third temperature profile, which specifies the temperature of the second cooling fluid in dependence on the cutting depth and in correlation with a third correction profile, which specifies the travel of the floating bearings in dependence on the cutting depth, wherein the third correction profile is opposite to the shape deviation.

5. The method of any of claims 1 to 2, wherein, During each of the cutting-off operations, the temperature of the workpiece is controlled by means of a closed control loop by wetting the workpiece with a cooling medium, wherein the temperature of the workpiece forms a controlled variable and the temperature of the cooling medium forms a manipulated variable of the control loop.

6. The method of claim 5, wherein, A constant temperature is specified as a reference variable of the control loop.

7. The method of any one of claims 1 to 2, wherein If the determined shape deviation reaches or exceeds a given threshold value before the corresponding cutting operation, a maintenance measure is initiated instead of the corresponding cutting operation.

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