OPERATING SAME

FIELD OF THE INVENTION

[0001] Embodiments of the present invention relate to a pulley for and in a wire saw device, a wire saw device, use of a wire saw device and a method for operating a wire saw device. More particularly, they relate to a pulley configured for a wire saw device, and a wire saw device for cutting or sawing hard materials such as blocks of silicon or quartz, e.g., for cutting silicon wafers, for a squarer, for a cropper or the like.

BACKGROUND OF THE INVENTION

[0002] Wire saw devices exist for cutting blocks or bricks, thin slices, e.g. semiconductor wafers, from a piece of hard material such as silicon. In such devices a stretched wire is fed from a spool and is both guided and tensioned by pulleys for guiding the wire in the cutting area. The wire that is used for sawing is generally provided with an abrasive material. As one option, the abrasive material can be provided as a slurry. This may be done shortly before the wire touches the material to be cut. Thereby, the abrasive is carried to the cutting position by the wire for cutting the material. As another option, the abrasive can be provided on the wire with a coating. For example, diamond particles can be provided on a metal wire, e.g. with a coating, wherein the diamond particles are imbedded in the coating of the wire. Thereby, the abrasive is firmly connected with the wire.

[0003] Generally, there is a tendency to use thinner wires in order to reduce the thickness of the cut and, thereby, to decrease the material wasted. There is also a desire to use diamond wires. These thinner wires and diamond wires are generally more susceptible to damage, and under high strain the wires may break more easily. Further, there is a desire to increase the cutting speed for improving the throughput of wire saw devices. The maximum speed for moving the piece through the web, and also the maximum effective cutting area within a given amount of time, is limited by several factors including wire speed, hardness of the material to be sawed, disturbing influences, desired precision, and the like. When the speed is increased, stopping of the machine gets increasingly difficult. Hence, the above-mentioned problems of avoiding damage or breakage of the wire are even more critical at higher sawing speeds.

SUMMARY

[0004] In view of the above, a pulley configured for a wire saw device having a wire forming a wire web according to independent claim 1, a wire saw device according to claim 14, and a method of operating a wire saw device according to independent claim 18 are provided. Further advantages, features, aspects and details are apparent from the dependent claims, the description and drawings.

[0005] According to one embodiment, a pulley configured for a wire saw device having a wire forming a wire web is provided. The pulley includes a wheel portion around the pulley axis, wherein the wheel portion includes electrically conductive plastic material and a wire guiding portion radially outward of the wheel portion having a groove structure for guiding the wire.

[0006] According to a further embodiment, a wire saw device having a wire forming a wire web is provided. The wire saw device includes a pulley configured for the wire saw device. The pulley includes a wheel portion around the pulley axis, wherein the wheel portion comprises electrically conductive plastic material and a wire guiding portion radially outward of the wheel portion having a groove structure for guiding the wire.

[0007] According to a yet further embodiment, a method of operating a wire saw device having a wire forming a wire web is provided. The method includes providing a plurality of pulleys having a wheel portion around the pulley axis, wherein the wheel portion includes electrically conductive plastic material, biasing the wire on an electrical potential, and monitoring existence of an electrical current in the wire saw device during contact of the wire with the wheel portion.

[0008] Embodiments are also directed at apparatuses for carrying out the disclosed methods and including apparatus parts for performing each described method step. These method steps may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the invention are also directed at methods by which the described apparatus operates. It includes method steps for carrying out every function of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the invention and are described in the following:

FIG. 1 shows a schematic view of a wire saw device according to embodiments described herein;

FIG. 2 shows a schematic view of a yet further wire saw device according to embodiments described herein;

FIG. 3 shows a perspective view of a wire management unit; and

FIGS. 4A and 4B show schematic views of a pulley illustrating embodiments of pulleys according to embodiments described herein; and

FIGS. 5 A and 5B show schematic views of a yet further pulleys according to embodiments described herein.

DETAILED DESCRIPTION OF THE INVENTION

[0010] Reference will now be made in detail to the various embodiments of the invention, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the invention and is not meant as a limitation of the invention. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations. [0011] Furthermore, in the following description a wire management unit will be understood as a device handling the supply of wire to a cutting area or working area of a wire saw device, such as a cropper, a squarer, or a wafer cutting wire saw. Typically, the wire saw includes a wire guide for transporting and guiding the wire in a wire moving direction while the wire management unit provides control of the wire tension. Furthermore, the wire provided by the wire management unit forms a wire web in the cutting area. Often, a wire web will be considered as the web formed by a single wire management unit. It should be understood that a wire web may contain more than one working area which is defined as an area in which a sawing process is performed. Thus, according to some embodiments described herein, a wire web can have multiple areas that are formed by a wire from different wire management units.

[0012] For modern wire saw devices like croppers, squarers, or wire saws, there is the desire to cut the hard material such as semiconductor material, for example silicon, quartz, or the like at high speeds. The wire speed, that is, the speed of the wire moving through the wire saw device, the wire management unit and the material to be sawed, respectively, can be, for example, 10 m/s or higher. Typically, the wire speed can be in a range of 15 to 20 m/s. However, higher wire speeds of 25 m/s or 30 m/s can also be desirable and could be realized under certain conditions.

[0013] For unwinding the wire at the desired wire speed, the spool rotates with a rotation speed of up to several thousands rotations per minute. For example, 1000 to 2000 rpm can be provided for unwinding the wire.

[0014] FIG. 1 shows a wire saw device 100. As can be seen from the pattern of the wire 10 forming the wire web in the wire web compartment 110, the example shown in FIG. 1 illustrates a squarer. The housing of the wire saw device is separated into different areas as indicated by the dotted line. The wire web is formed in the wire web compartment 110. Further, a housing portion 111, which houses further components and equipment of the wire saw device 100 is provided. For example, a wire handling device compartment 112 and an electrical cabinet 114 can be provided. Within the further housing portion 111, tanks 120 and 124 as well as respective pumps 121 and 125 can also be provided.

[0015] According to some embodiments, which can be combined with other embodiments described herein, the first tank 120 can be used for unused cooling fluid, e.g. in the case where the wire saw device is operated with diamond wire, or can be used e.g. for unused (fresh) slurry, in the case where the wire saw device 100 is operated with a wire requiring additional abrasive. The pump 121 pumps the cooling fluid (or slurry, respectively) towards the desired position in the cutting area. This is indicated in FIG. 1 by conduit 122. The used cooling fluid (or slurry) may flow back through conduit 126 and is pumped by pump 125 into the second tank 124. In those cases where cooling fluid or slurry is used, a portion of the used consumable fluid can be re-used if it is reinserted into the tank 120. Thus, according to different embodiments only a portion of the consumable fluid, all of the consumable fluid or none of the consumable fluid may be reused and, thus, be reinserted in tank 120. As one example, an additional valve might be provided in conduit 126 for selectively choosing the tank into which the used fluid is pumped. According to yet another example, a fluid connection between the tank 124 and 120 can be provided in order to reinsert a portion of the used fluid in tank 120. According to different embodiments, as already described above, the consumable fluid can be cooling fluid or slurry. Generally, if slurry is used, the slurry also takes over the function of cooling the position, at which the wire cuts the material.

[0016] In the wire handling compartment 112 two handling sections for delivering the wire 10 to the cutting area and receiving the wire from the cutting area, respectively, are provided. According to some embodiments, which can be combined with other embodiments described herein, the wire is provided on a spool 132 rotating around the spool axes 132a. The wire is guided over a plurality of rollers 134 into the wire web compartment 110. Further pulleys 134 and 136 guide the wire 10 in the cutting area to form the wire web. Thereby, further pulleys (not shown) are required to guide the wire 10 from one pulley 136 to a further pulley 136. In order to avoid unnecessary complexity, these further pulleys are not shown in FIG. 1. After cutting, the wire is guided by a further pulley 134 towards the wire handling compartment 112 and is therein provided over pulleys 134 on the spool 130 rotating around the spool axes 130a.

[0017] According to yet further embodiments, which can be combined with other embodiments described herein, the wire handling system can be adapted for bi-directional use, such that in one direction the wire is fed from spool 132 to spool 130 and in a further direction, the wire is fed from spool 130 to spool 132. Thereby, according to typical implementations the two units corresponding to spools 130 and 132 include similar components such as pulleys or the like, to have a corresponding wire handling in both sawing directions. The bi-directional use of the wire saw device may be of particular interest if diamond wire is used. [0018] Typically, the wire is guided from the wire handling compartment to the wire cutting area and back with a wire speed of 10 m/s or higher, typically in a range of 15 to 20 m/s. or even up to 25 m/s or 30 m s. The material to be cut is positioned on the support 140. The support 140 and the wire web defined by pulleys 136 can be moved relative to each other such that cutting of the material can be conducted. According to one embodiment, the pulleys 136 maintain in a fixed position and the support 314 moves the material to be cut through the wire web while the wire is at a speed of about 10 m/s or higher. For easier understanding, this movement of the support 140 would in FIG. 1 be perpendicular to the plane of the drawing. According to another embodiment, the pulleys 136 and, thus, the web generated by wire 10 is moved relative to the support 140 to cut the wire through the material. According to yet further embodiment, both the support 140 and the wire web can be both moved with respect to each other.

[0019] As indicated by the dotted lines in FIG. 1 the electrical cabinet 114 may serve to control the operation of the different components. For example, movement of the support 140, operation of the pumps 121 and 125, rotation of the spools 130 and 132 can be controlled. Further, additionally or optionally, the filling level of the tanks 120 and 124 can be measured and respective signals can be fed to the control unit. According to yet further embodiments, other control signals and monitoring signals can be fed to and from the electrical cabinet 114. For example, signals from the motors driving the spools, from a wire tensioner, to a wire tensioner, pressure signals for feeding the consumable fluids like slurry or cooling fluid, or a wire break detection signal can be fed to and from the electrical cabinet. Even though an electrical cabinet 114 integrated in a wire saw device 100 is shown in FIG. 1, it is apparent to a person skilled in the art that an electrical cabinet or a control unit in general can be provided at a different location in the wire saw device, e.g., also external of the wire device, and corresponding control signals from and to the control unit can be provided accordingly.

[0020] A further example of a wire saw device 200 is shown in FIG. 2. As can be seen from the wire web formed by the wire 10 in the wire web compartment 110, the system shown in FIG. 2 can be used to slice wafers, i.e. the system is a wire saw. According to the embodiments illustrated with respect to FIG. 2, two wire handling compartments 212a and 212b are provided. Each of the wire handling units feed the wire 10 towards the wire web and the wire is guided over pulleys 134 to form a wire web. As shown in FIG. 2, the wire web is formed by two adjacent areas wherein wire from each of the wire handling units is used to form one area of the wire web. As described above with respect to FIG. 1, pulleys 134 are provided for guiding the wire. Accordingly, embodiments that have been described with respect to FIG. 1, can correspondingly be formed for the wire saw device of FIG. 2.

[0021] According to different embodiments, a wire saw device can be a cropper, a squarer, a wire saw or a multiple wire saw. Thereby, a cropper is to be understood as a device, which can be used to saw end pieces from bricks or blocks, which have been separated into bricks in a squarer. A squarer is a wire saw that generally saws the silicon ingot into squares of the desired size such that a wire saw or a multiple wire saw can saw wafers from the bricks in a wafering process. The wire management unit herein is particularly useful for the wire saw device being a squarer, but not limited to a squarer.

[0022] The above-described systems are particularly useful if thin wires or wires with a coating, e.g. a diamond coating, are used. Accordingly, in embodiments which can be combined with other embodiments described herein, the wire handling sections and wire saw devices described herein are adapted for thin wires having a diameter below about 400 μηι, such as diameters between about 200 μιη and about 400 pm, more particularly between about 200 μπι and about 300 μπι. However, in other cases embodiments may also have a wire diameter as low as, for example, 100 μιη or even 80 pm. Further, the wire handling sections and wire saw devices described herein are adapted for coated wires, for example a wire having a nickel coating with diamond particles embedded therein. Such wires may typically have a diameter of about 300 μιη to about 400 μιη, e.g. 310 pm to 340 pm. For those wires a twisting of the wire might increase the risk of breaking of the wire or of damaging the coating, so that a twist-free operation is advantageous. By using diamond wire, the throughput may be increased by a factor of 2 or even more. In the case of a squarer, throughput rates of 100MW or even more can be achieved in this manner. When a diamond wire is used, further parts of the wire saw may be adapted to the diamond wire. For example, mechanical parts, electrical parts and/or software may be adapted to the use of diamond wire.

[0023] Typically, embodiments of pulleys described herein are adapted or configured for wire saw devices, they can be used in wire saw devices and/or can be a part of a wire saw device. Besides other aspects that can be used for making the pulley adapted or configured for a wire saw device, the pulley can have a groove structure which is made to guide a wire with a thickness of 400 pm or below, or a thickness of any of the other diameters mentioned above. Thereby, it has to be noted that the groove structure is designed specially for the wire diameter and the cutting process in order to allow for high precision cutting, e.g. with a precision of 250 μιη or below, or even of 50 μιη or below.

[0024] In the following, yet further embodiments are described, whose elements can be combined with any elements of other embodiments described herein. Within the following description, only those elements will be described, which deviate from those of previous or other embodiments described herein. It is to be understood that components, aspects and details described with respect to other embodiments can as well be applied to those embodiments which do not describe all components, aspects or details.

[0025] FIG. 3 shows a perspective view of a wire management unit according to some embodiments, which can be combined with other embodiments described herein. The embodiment of FIG. 3 includes a spool 312, mounted on spool shaft 310, and the pulleys 320, 330 and 340 are arranged to guide the wire, particularly with a wire tracking system. Examples of a wire tracking system are described in European patent application No. 09153051.9, entitled "Wire saw device and method for operating same" filed February 17, 2009, which is incorporated herein by reference to the extent the applications are not inconsistent with this disclosure. Additionally, a recess 116 can be seen. The recess 116 is provided in the main frame portion. The recess is dimensioned and arranged for accommodating at least partially the first pulley 320. This recess allows the first pulley 320 and, hence, the spool 312 to be arranged closer to the main frame portion while still allowing the first pulley 320 motion track to cover most or all of the wire carrying area 213a. Further, the pulley carrying unit 324 is provided as a retractable or telescopic bar. The retractable or telescopic bar is longitudinally movable along a bar axis parallel to the spool axis. The bar is longitudinally movably mounted to a wall portion of the main frame portion, e.g. a wall portion of the recess 116.

[0026] Further, in the embodiment of FIG. 3 the main frame portion includes a mounting member 314, to which the second and third pulley 330, 340 are mounted. The mounting member 314, being part of the main frame portion, is rigidly connected to the chassis of the wire saw device. While other designs of the mounting member are possible in the specific embodiment of FIG. 3, the mounting member is a bar, more specifically an L-shaped bar with a first leg 114a extending to a side surface of the main frame portion (i.e. extending parallel to the x axis), and with a second leg 114b forming an essentially right angle with the first leg and extending to a top surface of the main frame portion (i.e. extending parallel to the z axis). Independently from the shown embodiment, it is a general aspect that the first pulley 320 and the second pulley 330 (and, if present, optionally also other pulleys such as a third and/or fourth pulley) are mounted on a common mounting member, especially on a one-piece mounting member.

[0027] Further, a fourth pulley 350 is shown. The fourth pulley 350 receives the wire from the third pulley and redirects the wire by a fourth redirection angle. The fourth pulley 350 is rotatably mounted to the frame for rotation around a fourth pulley axis. Here, the fourth redirection angle is about 90°. In other embodiments, the fourth redirection angle may be between 60° and 120°. The fourth pulley axis is essentially parallel to the spool axis. Further, the fourth pulley axis is essentially perpendicular to the first pulley axis, the second pulley axis, and the third pulley axis. In other embodiments, the fourth pulley axis may be essentially parallel to at least one of these axes.

[0028] The embodiment of FIG. 3 further includes a wire tensioner for controlling the tension of the wire. The wire tensioner includes a fifth pulley 360 rotatably mounted to the frame for rotation around a fifth pulley axis 362 and a sixth pulley 370 rotatably mounted to a movable element 374 for rotation around a sixth pulley axis 372. The movable element 374 is movably mounted on the main frame portion. The movement of the movable element 374 may be controlled by a motor, or the movable element 374 may be pre-biased e.g. by a spring, for controlling the wire tension. In FIG. 3, the movable element 374 is shown as a pre-biased swivel lever. The wire tensioner receives the wire 10 from the fourth pulley 350 and provides the wire 10 to the wire web (to the right of the wire management unit shown in FIG. 3). More precisely, the fifth pulley 360 receives the wire 10 from the fourth pulley 350 and deflects the wire by a fifth deflection angle, and then the sixth pulley 370 receives the wire 10 from the fifth pulley 360 and deflects the wire by a sixth deflection angle.

[0029] With the x-y-z reference frame defined above, it is a general aspect, illustrated in the embodiment of FIG. 3, that at least one condition (and in some embodiments, even all conditions) selected from the following list is satisfied:

- the wire tensioner is on a side of the spool 312 essentially opposite of the first pulley 320;

- the wire between the fourth pulley and the wire tensioner, more specifically between the fourth and the fifth pulley, extends primarily along the z axis;

- the wire between the fifth pulley and the sixth pulley extends primarily along the y axis;

- the wire leaves the sixth pulley essentially parallel to the y axis;

- the fifth and sixth pulley having respective axes each extending essentially in the x direction; the fifth redirection angle is in the range of about 60° to 90°, especially in the range of about 80° to 90°; and/or

the sixth redirection angle is about 180°.

[0030] Generally, in embodiments which may be combined with other embodiments herein, the pulleys have at least one and in embodiments all of the following radiuses: The spool shaft 310 has a diameter of about 150 mm. The first pulley 320 and the second pulley 330 have a diameter of between 100 mm and 150 mm, especially of 112 mm (here, the diameter means the diameter observed by the wire, i.e. diameter within the wire guiding groove). The third pulley 340 has a diameter of between 140 and 170 mm, especially of 158 mm. The fourth pulley 350 has a diameter similar to the first pulley 320. The fifth pulley 360 and the sixth pulley 370 have a diameter similar to the third pulley 340.

[0031] Continuing the description of FIG. 3, besides the wire handling section 300, which in the following will also be called primary wire handling section 300, the wire management unit of FIG. 3 also has a secondary wire handling section 300b. Here, the terms "primary" and "secondary" are introduced for ease of identification, and do not imply and hierarchical or functional order of the wire handling sections, spools etc. The secondary wire handling section 300b is constructed similarly to the primary wire handling section 300 and has corresponding elements to the elements of the primary wire handling section 300. The elements of the secondary wire handling section 300b are denoted as "secondary" elements and assigned reference signs 310b, 312b etc. corresponding to the corresponding "primary" elements 310, 312 etc. of the primary wire handling section 300. Thus, the secondary wire handling unit 300b has e.g. a secondary spool shaft 310b for a spool 312b, a secondary first pulley 320b, a secondary second pulley 330b etc. The secondary first pulley 320b is rotatably mounted to a secondary pulley carrying unit 324b for rotation around a secondary first pulley axis 322b, the secondary pulley carrying unit being longitudinally movable along a secondary pulley motion track. The primary and the secondary wire handling sections 300, 300b are placed in y direction adjacent to each other. As a general aspect illustrated by, but independent of the shown embodiment, the primary and the secondary wire handling sections 300, 300b may be placed on a common wall portion of the main frame portion. Further, the primary and the secondary wire handling sections 300, 300b may be placed in a common compartment of the wire saw device. Further, it can be seen that in FIG. 3, the primary spool 312 is of a different type than the secondary spool 312b (as can be seen from the absence of slits in the front flange of the secondary spool 312b). [0032] Generally, the secondary wire handling section 300b is formed in the same manner as the wire handling section 300 according to any embodiment described herein. The description of elements of the primary wire handling section 300 is therefore also applicable to the corresponding elements of the secondary wire handling section 300b.

[0033] In an example mode of operation, henceforth called primary-to-secondary-spool sawing, the primary wire handling section provides wire from the primary first spool 312 to the web 10, so that the wire can be used for sawing in the web. Then, the secondary wire handling section 300b receives the wire 10 from the web. Thereby, the wire 10 is transported from the web to the secondary wire tensioner, more precisely to the secondary sixth pulley 370b and then to the secondary fifth pulley 360b, from there to the secondary fourth pulley 350b, from there to the secondary third pulley 340b, from there to the secondary second pulley 330b, from there to the secondary first pulley 320b, and from there finally is wound onto the spool 312b. Further, a controller controls the motion of the secondary first pulley 320b along the secondary pulley motion track so that the wire is wound in a controlled manner onto the wire carrying area of the secondary spool 312b.

[0034] For receiving the wire, a secondary first pulley controller includes a wire winding pattern and is programmed to determine a desired wire winding position for winding the wire on the wire carrying area of the secondary spool, and transmits a moving command to the secondary first pulley moving device 324b for causing the secondary first pulley moving device 324b to move the secondary first pulley 320b to the desired wire winding position.

[0035] The secondary second pulley 330b redirects the wire by about 180°, and the secondary first pulley redirects the wire by about 90°. Due to the large secondary second pulley 330b redirection angle, sharp tensions and vibrations during winding of the wire are avoided, as explained above, so that the wire can be securely wound with reduced risk of wire damage. Therefore, the secondary second pulley 330b may redirect the wire by not less than 60°, and the secondary first pulley redirects the wire by not more than 120°.

[0036] Generally, the spools in which new wire is provided are of a different type (say, a first spool type) than the spools onto which the used wire is wound (say, a second spool type). For example, the spools in which new wire is provided may be disposable spools from a wire manufacturer. Such spools may, on the other hand, be unsuitable for receiving used wire because they sometimes do not withstand the high wire tension of the used wire. In order to support these different spool types during primary-to-secondary-spool sawing, the primary spool shaft (i.e. the spool shaft of the primary wire handling section) may be adapted for carrying a spool of the first type, and the secondary spool shaft (i.e. the spool shaft of the secondary wire handling section) is adapted for carrying a spool of the second type, i.e. the second type being different from the first type.

[0037] Also, in some embodiments, which can be combined with any other embodiments herein, the wire management section may support bidirectional sawing. Herein, bidirectional sawing is understood to be a sawing process during which first the wire is transported from the primary spool to the secondary spool, and thereafter is transported back from the secondary spool to the primary spool, and again from the primary spool to the secondary spool etc. Thus, for bidirectional sawing the (primary) spool 312 is adapted for providing wire to the wire web and is also adapted for receiving used wire from the wire web. Likewise, a secondary spool 312b may be adapted for providing wire to the wire web and is also adapted for receiving used wire from the wire web.

[0038] For the bidirectional sawing, a controller is adapted for sending actuating commands to the primary spool shaft and to the secondary spool shaft, the actuating commands causing, in a first step, the first spool shaft to unwind wire to the second spool, and causing, in a second step, the second spool shaft to unwind wire to the first spool.

[0039] The above-described arrangements of the pulleys are particularly useful if thin wires or wires with a coating, e.g. a diamond coating, are used. Accordingly, in embodiments, which can be combined other embodiments described herein, the wire handling sections and wire saw devices described herein are adapted for thin wires having a diameter below about 400 μιη, such as diameters between about 200 μιη and about 400 μπι, more particularly between about 200 μιη and about 300 μιη. However, in other cases embodiments may also have a wire diameter as low as for example 100 μπι or even 80 μιη. Further the wire handling sections and wire saw devices described herein are adapted for coated wires, for example a wire having a nickel coating with diamond particles embedded therein. Such wires may typically have a diameter of about 300 μπι to about 400 μιη, e.g. 310 μπι to 340 μηι. For those wires a twisting of the wire might increase the risk of breaking of the wire or of damaging the coating, so that a twist- free operation is advantageous. By using diamond wire, the throughput may be increased by a factor of 2 or even more. In the case of a squarer, throughput rates of 100MW or even more can be achieved in this manner. [0040] When a diamond wire is used, further parts of the wire saw may be adapted to the diamond wire. For example, mechanical parts, electrical parts and / or software may be adapted to the use of diamond wire.

[0041] As described above, a plurality of pulleys are used in wire saw devices described herein. Thereby, it has to be taken into account that there is the desire for higher cutting speeds and, thereby, higher wire speeds, a desire for thinner wires or different types of wires, such as diamond wires ^' , and improved device control at the facility of the customer. During sawing operation the pulleys generally rotate fast around their respective axes. According to some embodiments, the pulleys are adapted for wire saw devices by being capable of rotation speeds of 2000 rpm and more, or even 3000 rpm or more, e.g., 2000 rpm to 4000 rpm. For example, during an emergency stop the wire saw device needs to be stopped as fast as possible. Thereby, however, the inertia of the pulleys, that is the moment of inertia of the pulleys, result in the pulleys rotation not to stop immediately. This further pulley rotation may result in a harmful tension on the wire such that wire breakage may occur.

[0042] Further, according to some embodiments, which can be combined with other embodiments described herein, such a wire breakage can be detected as follows. The wire is biased to the potential having an absolute value of about 20 V to 120 V, such as 30 V to 60 V. Thereby, a voltage between the wire and remaining wire saw device components such as the housing, the mainframe, the pullies, housing portions, or doors of cabinets, and the like is generated. For example, these further components can be on ground potential. If the wire breaks, the loose end of the wire touches one of the components of the wire saw device. The voltage between the wire and the wire saw device results in a current. Accordingly, a wire breakage detection system can monitor the existence of such a current and detect the breakage of the wire if such a current is detected.

[0043] As a yet further aspect, the increasing cutting speeds and the use of thin wires according to embodiments described herein and different types of wires, such as diamond wires, result in an increased desire to avoid even small vibrations in the wire saw device. On the one hand, this can be done by improved wire handling units. Examples of a wire handling unit are described in co-pending application of the applicant, which is filed on the same day as the: present application and which is entitled "WIRE HANDLING UNIT, WIRE SAW

DEVICE AND METHOD FOR OPERATING SAME", which is incorporated herein by reference to the extent the applications are not inconsistent with this disclosure.. On the other

RECTIFIED SHEET (RULE 91) ISA/EP hand the tendency of pulleys and other means for guiding the wire through the wire saw device to bend or to be instable should be reduced.

[0044] Common pulleys for guiding the wire through the wire saw device are made out of metal, for example aluminum, so that they provide conductivity for a wire break detection system. Aluminum pulleys have a comparably low mass as compared to other metal pulleys. The still further increasing demand for faster cutting, thinner wires, faster wire break detection and new types of wires, for example diamond wires, bring the desire for even further improvements. According to embodiments described herein, pulleys are made of an electrically conductive plastic material. Thereby, the mass and, thus, the moment of inertia can be further reduced, electrical conductivity for wire breakage detection can be provided and a deformation of the wire during maintenance and/or operation can also be reduced. Accordingly, a lower moment of inertia and smoother spinning can be provided while being capable of having a wire break detection current flowing through the pulley.

[0045] FIGS. 4A and 4B illustrate some embodiments of pulleys according to embodiments described herein. The pulley 400 has a wheel portion 410 and a tire portion 450, which is provided radially outward of the wheel portion 410. Thereby, the wheel portion or at least 80% of the wheel portion is made of a material consisting essentially of electrically conductive plastic material. According to yet further embodiments, which can be combined with other embodiments described herein, the tire can be a separate component, which is detachably connectable to the wheel portion.

[0046] As shown in FIG. 4A openings 412 can be provided in the wheel portion 410 such that for example a spoke structure is provided in the wheel portion. This can further decrease the weight and thus the moment of inertia of the pulley 400. The wheel portion 410 may further have a bearing receiving portion 414. Thereby, the bearing receiving portion 414 is adapted for receiving a bearing that can be used at 2000 rpm and more, or even 3000 rpm or more, e.g., 2000 rpm to 4000 rpm. A tire 450, which is made of an insulating material, is provided radially outward of the wheel portion 410. Typically, the tire, which provides a wire carrying portion of pulley 400, includes one or more grooves for guiding the wire. Since the tire 450 is electrically insulating, the wire 10, which is biased to a potential, is electrically insulated from the wheel portion 410. If the wire is biased by a power supply 470, as shown in FIG. 4A, and the loose end of the wire 10 touches the pulley at the wheel portion 410 after breakage, which is indicated in FIG. 4A, a current can be detected by a measurement device 472. [0047] A cross-sectional view illustrating yet further embodiments of the pulley 400 is shown in FIG. 4B. In FIG. 4B the wheel portion 410 is configured to rotate around the axis 410a. The wheel portion has a tire carrying portion 420. The tire 450 is mounted on the wheel portion 410, that is radially outward of the wheel portion. As shown in FIG. 4B a groove 452 is provided in the wire guiding portion (tire 450) such that the wire is guided on the pulley 400. Groove 452 defines, as indicated in FIG. 4B, a plane 462 which is indicated by dotted lines. The wire is guided in plane 462 during rotation of the pulley. According to some embodiments, which can be combined with other embodiments described herein, the wheel portion has protrusions 422 or recesses (not shown) such that the pulley 410 is fully balanced with respect to plane 462 in which the wire is guided. For example, the protrusion 422 can compensate for the tire receiving portion 420. The center of mass can be located in the wire guiding plain 462. In FIG. 4B this is indicated by arrow 460 symbolizing a weighing scale. Since the center of mass is in the wire guiding plain 462 the pulley 400, which would be supported on a pivot point 460 as shown in FIG. 4B, is balanced.

[0048] In light of the above, smooth spinning can be further improved and the probability for vibrations can also be reduced. The manufacturing of the pulley from plastic material such as plastic material being formed in a mold, allows for optimized design and balance of the pulley without significantly increasing the manufacturing costs.

[0049] According to embodiments, which can be combined with other embodiments described herein, the pulley includes electrically conductive plastic material. For example, the pulley includes a wheel portion with electrically conductive plastic material or a wheel portion made out of electrically conductive plastic material. Thereby, according to some optional embodiments, the conductive plastic material has a density of 2.57 g/cm ³ or less, for example of 2.00 g/cm ³ or less. According to yet further optional modification. The density can be 1.5 g/cm ³ or less, for example from 1.0 g/cm ³ to 1.5 g/cm ³ . According to yet further embodiments, which can be combined with other embodiments described herein, the plastic material is a synthetic polymeric material including electrically conductive fibers. For example, the polymeric material can be polyamid and/or the electrically conductive fibers can be carbon fibers.

[0050] Thereby, the carbon fibers also increase the stiffness of the pulley or the wheel portion, respectively. For example, the bending moment at the periphery of the wheel portion can be reduces as compared to a bending moment of a corresponding alumiun pulley. Further damages to the wheel and a resulting loss of balance of the wheel with respect to the wire guiding plane can be reduced by a yield strength of 200 to 600 MPa, for example 300 to 500 MPa.

[0051] The material properties of the electrically conductive plastic material allow for a further reduction of the weight by providing a wheel portion with spokes or wheel portion openings for reducing the overall weight of the pulley. According to different embodiments, for example, 3 to 10, typically 6 to 8 openings can be provided in the wheel portion. Thereby, according to yet further optional embodiments, the moment of inertia can be 5.0*10 ⁴ kg*m ² or less, for example 3.5*10 ^~4 kg*m ² or less, such as for example from 1*10 ^~4 kg*m ² to 3.5*10 ^{" 4} kg*m ² . This may, according to yet further embodiments and in pulley diameter ranges configured for wire saw devices, be also described as the weight per diameter being 730 g/m or less, typically 500 g/m or less, more typically from 300 to 500 g/m.

[0052] In light of the above, the weight of the pulleys can, for example be reduced by 5% to 20% as compared to aluminum pulleys. Thereby, the electrically conductiveness is given by electrically conductive fibers such as carbon fibers which are embedded in the plastic material. For example carbon fiber charged polyamide can be used. The improved possibility to manufacture an essentially perfectly balanced pulley, that is the pulley which has the center of mass in the wire guiding plane, can further be used for smoother spinning and reduction of vibrations. This property can further be improved by a reduction of bending and deformation during maintenance, for example when forcing the tire on the wheel portion or damages by dropping the pulley or the like.

[0053] As described above the pulleys according to embodiments described herein are adapted or configured for use in a wire saw device. Thereby, one or more of the following properties can be provided: the pulley is adapted for rotation of at least 2000 rpm or even at least 3000 rpm; the pulley includes a bearing receiving portion for receiving a bearing which is adapted for rotation with at least 2000 rpm or even at least 3000 rpm; the wheel portion of the pulley has a tire receiving portion for receiving the tire with a groove structure for guiding the wire; the pulley includes a groove structure with grooves adapted for wires having a diameter of 400 μιη or less; a tire with one or more grooves is provided, wherein one of the grooves, typically a center groove, defines a wire guiding plane; the wire is balanced, that is as the center of mass in the wire guiding plane; the wheel portion of the pulley has a diameter in the range of 70 to 300 mm, for example 100 to 200 mm, or the like. [0054] FIGS. 5A and 5B illustrate yet further embodiments of pulleys according to embodiments described herein. The pulley 500 has a wheel portion 410 and a tire portion 450, which is provided radially outward of the wheel portion 410. Thereby, the wheel portion or at least 80% of the wheel portion is made of a material consisting essentially of electrically conductive plastic material.

[0055] As shown in FIG. 5 A and already described with respect to FIGS. 4, openings 412, typically 6 to 8 openings, can be provided in the wheel portion 410 such that for example a spoke structure is provided. This can further decrease the weight and thus the moment of inertia of the pulley 500. The wheel portion 410 may further have a bearing receiving portion 414. Thereby, the bearing receiving portion 414 is adapted for receiving a bearing that can be used at rotation speeds of 2000 rpm and above, or even 3000 rpm or more, e.g., 2000 rpm to 4000 rpm. A tire 450, which is made of an insulating material, is provided radially outward of the wheel portion 410 on a tire receiving portion 420. Typically, the tire, which can provide a wire guiding portion of pulley 400, includes one or more grooves, typically one groove, for guiding the wire.

[0056] A cross-sectional side view illustrating yet further embodiments of the pulley 500 is shown in FIG. 5B. The wheel portion 410 has a tire carrying portion 420. The tire 450 is mounted on the wheel portion 410, that is, adjacent to the wheel portion. As shown in FIG. 5B a groove 452 is provided in the wire guiding portion of the pulley. Groove 452 defines, as indicated in FIG. 5B, a plane 462. The wire is guided in plane 462 during rotation of the pulley. According to some embodiments, which can be combined with other embodiments described herein, the wheel portion has protrusions 422 or recesses (not shown) such that the pulley 410 is fully balanced with respect to plane 462 in which the wire is guided. For example, the protrusion 422 can compensate for the tire receiving portion 420 such that the center of mass is located in the wire guiding plain 462.

[0057] According to yet further embodiments, which can be combined with other embodiments described herein, a pulley can have a fixation opening for fixing the wire to a bearing. Thereby, as a further option alignment openings, such as openings 416 or 416' can be provided. As shown in FIGS. 5 the edges of the openings 412, the edges of the tire receiving portions and other structures, for example protrusion and recess in the pulley can be rounded or have rounded edges with a radius of curvature of several mm, e.g., at least 1 mm or 2 mm to 5 mm. This may further reduce the weight and might improve the pulley behavior during fast spinning. Additionally, slurry, cooling fluid, or other solid particles from the process can not sediment at the pulleys as compared to a corresponding shape having sharp edges.

[0058] According to yet further embodiments, which can be combined with other embodiments described herein, the plastic material included in the pulley can be resistant to polyethylene glycol, water based coolants adapted for sawing in a wire saw device, e.g. with diamond wire, and/or combinations thereof.

[0059] In the following, some general aspects of the embodiments described herein will be summarized. Each of these general aspects can be combined with any other general aspect, within any embodiment described herein, to generate yet another embodiment.

[0060] According to one embodiment, a pulley configured for a wire saw device having a wire forming a wire web is provided. The pulley includes a wheel portion around the pulley axis, wherein the wheel portion comprises electrically conductive plastic material, and a wire guiding portion radially outward of the wheel portion having a groove structure for guiding the wire.

[0061] According to one optional aspect, which can be provided for pulleys for wire saw devices, and wire saw devices described herein, the conductive plastic material can have a density of 2.00 g/cm ³ or less, typically 1.5 g/cm ³ or less, more typically from 1.0 g/cm ³ to 1.5 g/cm ³ . Accordingly, as a further alternative or optional aspects the moment of inertia can be 5.0*10 ^"4 kg*m ² or less, typically 3.5*10 ^~4 kg*m ² or less; and/or the weight per diameter can be 730 g/m or less, typically 500 g/m or less, more typically from 300 to 500 g/m.. As described above, this can result in a reduced wire breakage probability, especially during stop or emergency stop of the wire saw device, during which the inertia of pulleys might generate additional tension on a wire. These and other aspects might particularly useful for diamond wire or thin wires as described herein, wherein wire breakage needs to be effectively reduced.

[0062] Thereby, for some embodiments, which can be combined with other embodiments described herein, a wire saw device and/or a pulley for a wire saw device can be adapted for diamond wire, and methods of operating can be performed with diamond wire. This can, for example, be done by adapting the groove structure with an appropriate pitch of grooves, a different depth of grooves and/or a different shape of grooves. By using diamond wire, typically the cutting speed can be increased, e.g., by a factor of 2, the energy consumption of the wire saw device can be reduced and, further, as yet another example, the costs of squaring silicon ingots or wafering silicon can be significantly reduced.

[0063] According to yet further optional aspects, which can be combined with embodiments described herein, the yield strength of the pulley can be 400 MPa or more; and/or the bending moment can be reduced as compared to a corresponding aluminum pulley. According to yet further alternative or additional implementations, the plastic material can be a synthetic polymeric material including electrically conductive fibers, e.g. the polymeric material can be a polyamide, the pulley can include carbon fibers; and/or the plastic material can be chemical stable with respect to polyethylene glycol, water based coolant liquids adapted for a wire saw device, and mixtures thereof.

[0064] According to yet another optional aspect, which can be provided for embodiments described herein, the wire guiding portion can include a tire, can be provided as a tire or with a tire respectively. Typically, the wire guiding portion can be separate from the wheel portion. For example a tire can be provided on the wheel portion. According to yet further embodiments, which can be combined with other embodiments described herein, the groove structure can be one or more circumferential grooves, wherein one of the grooves or the one groove defines a wire guiding plane. Thereby, for example, the center of mass of the pulley can be located within the wire guiding plane

[0065] According to a yet further embodiment, a wire saw device with a pulley according to any of the embodiments described above is provided. Thereby, as one optional aspect, essentially all pulleys have essentially the same moment of inertia. For example, the moment of inertia of the pulleys does not deviate from each other more than 10 % or more than 5 %. Typically, according to different implementations, the wire saw device can be an element selected from the group consisting of: a wire saw, a multiple wire saw, a squarer, and a cropper. According to yet further embodiments, which can be combined with other embodiments described herein, the wire saw device can further include a main body of the wire saw device, a voltage supply adapted for biasing the wire on an electrical potential and an electrical conductive path from the wheel portion of the pulley to the main body.

[0066] According to a yet further embodiment, a method of operating a wire saw device having a wire forming a wire web is provided. The method includes providing a plurality of pulley having a wheel portion around the pulley axis, wherein the wheel portion comprises electrically conductive plastic material, biasing the wire on an electrical potential, and monitoring existence of an electrical current in the wire saw device during contact of the wire with the wheel portion. Thereby, the pulley can according to different implementation be provided according to any of the embodiments described herein. According to a yet further aspect, which can be combined with embodiments described herein, the method can further include moving the wire towards and from the wire web, wherein the wire is guided by the plurality of pulleys, stopping movement of the wire in the wire saw device upon a signal that existence of the electrical current has been detected.

[0067] According to a further aspect, a wire management unit can include a first pulley wire tracking system allowing actuation of a first pulley moving device in response to a detected wire position. According to a further aspect, the first pulley wire tracking system includes: a first pulley moving device being at least one element selected from the group of a linear actuator, a linear motor, a pneumatic cylinder, and a motor with a worm drive; a wire position detection device adapted for detecting the wire position along the direction of the motion path; a first pulley position controller being operatively connected to the wire position detection device for receiving the detected wire position, and being adapted for determining a target position, and being operatively connected to the first pulley moving device for transmitting a moving command causing the first pulley moving device to move the first pulley to the target position.

[0068] According to a further aspect, the wire management unit is adapted for the wire being a diamond wire, i.e. including diamonds. According to a further aspect, a main frame portion is rigid, and rigidly connectable or connected or integral with the chassis of the wire saw device.

[0069] According to a further aspect, a spool is adapted for providing wire to the wire web and is also adapted for receiving used wire from the wire web. According to a further aspect, the spool has a wire carrying area, and the first pulley position controller includes a wire winding pattern and is programmed for determining a target position, and being operatively connected to the first pulley moving device for transmitting a moving command thereto for causing the first pulley moving device to move the first pulley to the target position. According to a further aspect, the wire handling section is a primary wire handling section, the wire management unit further including a secondary wire handling section. According to a further aspect, the primary wire handling section has a spool shaft that is adapted for carrying a spool of first type, and the secondary wire handling section has a spool shaft that is adapted for carrying a spool of second type. [0070] According to a further aspect, a wire saw device is provided, the wire saw including a wire management unit according to any one of the embodiments described herein, wherein the main frame portion is rigidly connected to a chassis of the wire saw device. According to a further aspect, the wire saw device is an element selected from the group consisting of a wire saw, a multiple wire saw, a squarer, and a cropper. The present pulleys, wire management units and wire handling units can be particularly useful for a squarer.

[0071] While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.