METHOD FOR SAWING

FIELD OF THE INVENTION

[0001] Aspects of the present invention relate to a wire saw device and a method for operating such a wire saw device. More particularly, aspects of the present invention relate to 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 wire guide cylinders. 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 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, the wire is provided on a spool. Such a spool is provided from the wire supplier and may store several kilometers of wire. An example of such a supplier's spool is the model TA100 spool. During sawing, the wire is unwound from the supplier's spool and wound on another empty spool, called a take-up spool. The TA100 spool is generally not suitable as a take-up spool, since it is not strong enough to withstand the considerable load due to the wire tension of the wire to be wound thereon. Hence, a take-up spool of a customized design is used. So, a wire saw apparatus has generally two different spool shafts, one supply shaft adapted for receiving the TA100 wire supply spool, and one take-up shaft adapted for receiving the take-up spool. [0004] Mounting and unmounting the spools is generally time-consuming and requires specialized tools. Further, in addition to the supply and disposal management of the wire, also the spool supply and disposal must be managed. This is time and labor intensive. Further, the saw apparatus is stopped during the supply or disposal of spools and wire, which adds to the down-time of the wire spool saw.

SUMMARY

[0005] In view of the above, a wire saw device according to independent claims 1 and 25, and a method according to independent claims 21 to 23 are provided. Further advantages, features, aspects and details are apparent from the dependent claims, the description and drawings.

[0006] According to one embodiment, a wire saw device adapted for accommodating a wire forming a wire web for cutting is provided. The wire saw device has a wire handling section including a spool shaft adapted for carrying a wire spool, the spool shaft being rotatable about a spool axis and having at least one expandable surface section, the at least one expandable surface section being expandable essentially in a radial direction away from the spool axis for tightening the wire spool on the spool shaft.

[0007] According to a further embodiment, a method of mounting a wire spool on a spool shaft of a wire saw device is provided. The spool shaft is rotatable about (i.e. around) a spool axis. The method includes: axially putting the wire spool on the spool shaft from an axial free end of the spool shaft; and expanding at least one expandable surface section of the spool shaft essentially in a radial direction away from the spool axis, thereby tightening the wire spool on the spool shaft such that the wire spool tightly fits on the spool shaft. According to a further embodiment, a method of unmounting a wire spool from a spool shaft of a wire saw device is provided, which is essentially the inverse of the above-described method.

[0008] According to a further embodiment, a method of unmounting a wire spool from a spool shaft of a wire saw device is provided. The spool shaft is rotatable about a spool axis, the method includes: retracting at least one expandable surface section of the spool shaft essentially in a radial direction towards the spool axis, thereby loosening the wire spool from the spool shaft such that a clearance is produced between the wire spool and the spool shaft; and axially pulling the wire spool from an axial free end of the spool shaft. [0009] According to a further embodiment, a method of sawing using a wire saw device is provided. The wire saw device has a first wire spool shaft and a second wire spool shaft. The method includes: mounting a first wire spool on the first wire spool shaft, the first wire spool being of a first type and carrying wire saw wire; unwinding the wire from the first wire spool onto a second wire spool mounted on the second spool shaft; unmounting the first wire spool from the first spool shaft; mounting a third wire spool on the first wire spool shaft; and carrying out bi-directional sawing by the wire.

[0010] According to a further embodiment, a wire saw device adapted for accommodating a wire, the wire forming a wire web for cutting is provided. The wire saw device has a first spool shaft adapted for carrying a wire spool and a second spool shaft adapted for carrying a second wire spool, and a controller containing program code adapted for controlling the wire saw to perform at least one of the methods described herein.

[0011] 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

[0012] So that the manner in which the above recited features of aspects of the present invention can be understood in detail, a more particular description of aspects of the invention, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to the following:

Fig. la to lc are schematic cross-sectional side views of a spool shaft during mounting of a spool thereon according to a mounting method described herein for illustrative purposes;

Fig. 2a to 2c are schematic cross-sectional side views of a spool shaft according to an embodiment, during mounting of a spool thereon; Fig. 3 is a perspective view of a wire spool shaft of a wire saw device being an embodiment;

Fig. 4 is a schematic side view of a wire handling section of a wire saw device according to a further embodiment;

Fig. 5a to 5f are schematic side views of a wire saw device according to an embodiment, during sawing; and

Fig. 6 is a perspective view of a portion of a wire saw device according to an embodiment.

DETAILED DESCRIPTION

[0013] 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 the same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of aspects 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.

[0014] Furthermore, in the following description a wire management unit will be understood as a device handling the supply of wire to a 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 as described above. In the following, 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.

[0015] With reference to Figs, la to lc, a method of mounting a wire spool on a wire spool shaft will be described for illustrative purposes. The method of Figs, la to lc will serve as a background, so that the advantages of e.g. the embodiments shown in Fig. 2a to 2c will become more apparent by comparison. Fig. la shows, in cross-sectional side view, a wire spool shaft 110 that is rotatably mounted on a frame portion of the wire saw, for rotation about a spool axis 112a. The frame portion, not shown in Fig. la, is on the right side of the shaft 110, so that the left side of the shaft 110a is free. Further, the shaft 110 has a conical end piece 111 at the frame portion side. Generally, the elements shown in Figs, la to lc are essentially axially symmetric about the spool axis 112a.

[0016] Now referring to Fig. lb, a wire spool 112 having a wire carrying area 113a is put on the shaft, from the free shaft side 110a. The inner spool diameter is slightly larger than the outer shaft diameter, so that there is some clearance allowing the spool to be put on the shaft. Then, for tightly fitting the spool on the shaft, a conical end piece 182 is mounted onto the free shaft side by a screw 184. As is shown in Fig. lc, the screw 184 is then tightened such as to press the conical end piece 182 against the wire spool 112. Thereby, the spool 112 is clamped or fastened between the conical end pieces 111 and 182. To this purpose, the spool has contact surfaces form- fitted to the respective conical end pieces 111 and 182. During the clamping, the spool is also centered about the spool axis 112a.

[0017] The above method requires a large number of independent parts such as the spool 112, the shaft 110, the conical end piece 182, and the screw 184. Further, it is important to tighten the screw 184 sufficiently so that the spool is securely fastened between the conical end pieces 111 and 182. On the other hand, the screw 184 must not be tightened too tightly, because otherwise the shaft and the spool may be worn-out or even damaged. Hence, it is difficult to tighten the screw 184 to a sufficient degree. Generally, a customized dynamometric wrench is needed for this purpose, which further adds to the number of parts needed. Further, the method is time-consuming and labor-intensive, especially when taking into account the sometimes considerable weight of the wire spool 112. Further, for each spool type a specially adapted shaft is needed, with the dimensions of the shaft and of the conical end pieces being adapted to the spool.

[0018] Figs. 2a to 2c are schematic side views of a spool shaft according to an embodiment of the invention, by which at least some of the above disadvantages are reduced. The spool shaft 210 shown in cross-sectional side view in Fig. 2a is rotatably mounted on a frame portion of the wire saw, for rotation about a spool axis 212a. The frame portion, not shown in Fig. 2a, is on the right side of the shaft 210, so that the left side of the shaft 210a is free, i.e. adapted to receive a spool. Further, the shaft 210 has an optional conical end piece 211 at the frame portion side which serves as a stop collar for the spool. Generally, most elements shown in Figs. 2a to 2c are essentially axially symmetric about the spool axis 212a except where noted otherwise. Further, the shaft 210 has expandable surface sections 282. These expandable surface sections 282 are not axially symmetric, but may be provided e.g. at regular circumferential intervals about the spool axis 212a. The expandable surface sections 282 are arranged on the cylindrical outer surface of the shaft 210, and are expandable essentially in a radial direction away from the spool axis 212a. In Fig. 2a, the expandable surface sections 282 are shown in a retracted state. The expandable surface sections 282 are arranged in two circumferential rows about (i.e. around) the spool axis 212a, one row being closer to the frame portion side (i.e. to the conical end piece 211), and the other row being closer to the free side 210a. In the cross-sectional view of Fig. 2a, only two expandable surface sections 282 per row can be seen, but there may be more expandable surface sections 282. The arrangement of the expandable surface sections 282 in Fig. 2a only serves as an example, and any other arrangement may be chosen.

[0019] For mounting the wire spool on the spool shaft 210, the wire spool is axially put onto the spool shaft 210 from the free spool shaft side 210a. Fig. 2b shows the spool 212 having a wire carrying area 213a being put onto the spool shaft 210 such that the spool shaft 210 completely passes through the spool 212. The wire spool 212 is thus put fully onto the shaft, almost to the conical surface 211 serving as an end stop. After the spool has been put on the shaft, in Fig. 2b the free end 210a of the spool shaft 210 even extends slightly further outward (to the left) than the wire spool 212. The inner spool diameter of spool 212 is slightly larger than the outer shaft diameter of shaft 210, so that there is some clearance allowing the spool 212 to be put on the shaft 210. The clearance is shown on the lower side of the shaft in Fig. 2b, due to gravity.

[0020] Then, as shown in Fig. 2c, the expandable surface sections 282 of the spool shaft 210 are expanded, i.e. moved outwardly from the spool surface essentially in a radial direction away from the spool axis 212a. Due to this expansion, the wire spool 212 is thereby tightened on the spool shaft 210 such that the wire spool 212 tightly fits on the spool shaft 210. Due to the tightening, the spool is also lifted such as to be centered about the spool axis 112a.

[0021] Likewise, the expandable surface sections 282 can be used for a method of unmounting a wire spool 212 from the spool shaft 210. Such unmounting proceeds essentially as the inverse of the above-described mounting and includes: retracting at least one expandable surface section 282 of the spool shaft 210 essentially in a radial direction towards the spool axis 212a, thereby loosening the wire spool 212 from the spool shaft 210 such that a clearance is produced between the wire spool 212 and the spool shaft 210; and axially pulling the wire spool 212 from an axial free end 210a of the spool shaft 210.

[0022] In related embodiments, the arrangement of the expandable surfaces 282 may be different from the two-row arrangement shown in Figs. 2a to 2c. For example, only one row or three rows may be provided. Also, instead of rows the expandable surface sections may be arranged e.g. in a zig-zag pattern. Further, any other end stop can be provided in place of the conical end stop 211. Also, no conical end stop at all may be needed. Further, instead of a cylindrical shaft also a non-cylindrical shaft may be provided. Further, some other e.g. radial movement may be superimposed on the axial expansion of the surface sections 282.

[0023] Fig. 3 is a perspective view of a further wire spool shaft 210. The wire spool shaft 210 is essentially cylindrically shaped. Further, a stopper end face 211 is rigidly connected to the spool shaft 210 so that it rotates along with the spool shaft 210. The stopper end face 211 is essentially flat and orthogonal to the spool axis (i.e. to the cylinder axis of the spool shaft 210). The spool shaft 210 is mounted to a main frame portion of the wire saw device at the stopper end face 211 side of the spool shaft. The spool shaft 210 is rotatably mounted by bearings (not shown) allowing the spool shaft 210 to rotate about the spool axis. Further, a motor is connected to the spool shaft to drive the rotation of the spool shaft. The end 210a of the spool shaft 210 that is not mounted to the main frame portion is referred to as the free end, or as the spool receiving axial end.

[0024] The spool shaft 210 further has expandable surface sections 282, whose function is analogous to that of the corresponding surface sections described in conjunction with Figs. 2a to 2c. The expandable surface sections 282 are arranged in two circumferential rows about the spool axis. Further, the two rows are staggered with respect to each other. Furthermore, an actuator screw 284 is arranged at the free end 210a of the spool 210. By turning the actuator screw 284 in a first direction, the expandable surface sections 282 are expanded. By turning the actuator screw 282 in a second direction opposite to the first direction, the expandable surface sections 282 are retracted towards the spool axis. Thus, the actuator screw 282 acts as an external actuation input member, receiving an actuation force (namely, the force by which the screw is turned) which is responsible for actuating the expansion of the expandable surface sections 282 away from the spool axis.

[0025] The actuator mechanism for transmitting the rotation of the actuator screw into an expansion of the expandable surface sections 282 is not shown in Fig. 3. A number of different mechanisms can be used. For example, the rotation of the screw may be transmitted e.g. by a bolt-nut type gear into a longitudinal movement of a moving element (e.g. attached to the nut) along the spool axis. Then, the moving element has for each of the surface sections 282 a surface profile so that during longitudinal motion of the moving element, the surface sections 282 are pressed outwardly and thus expanded according to the surface profile. As another example, an adjustable spring member may be attached to the expandable surface sections 282. The actuator screw 284 may be connected to the adjustment mechanism of the adjustable spring member so that, when the actuator screw 284 is turned in the first direction, it adjusts the biasing of the adjustable spring member to bias the expandable surface sections 282 in an expansion direction away from the spool axis. As another example, the actuator screw 284 may be connected to a hydraulic reservoir so that the hydraulic reservoir is compressed when the actuator screw 284 is turned in the first direction. Then, the surface section 282 may also be connected to the hydraulic reservoir so that the surface section 282 is expanded when the hydraulic reservoir is compressed.

[0026] Further, other external actuation input members can be used instead of the actuator screw 282. For example, a pneumatic input valve may be provided at the free shaft end 210a, and a pneumatic conduit may be provided within the shaft so that the surface sections are lifted by pressurized air inputted to the pneumatic input valve from the outside.

[0027] 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, e.g. TA100 type spools. 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. The spool shaft according to the embodiment of Fig. 4 is adapted for carrying such different spool types, i.e. for carrying a spool of first type and for carrying a spool of second type, the second type being different from the first type. Preferably, the spools all have a similar inner diameter (e.g. about 150 mm, which is the inner diameter of a TA 100 spool), so that changeover of spools is fast and hence efficient.

[0028] Fig. 4 is a schematic side view of a portion of a wire handling section of a wire saw device 1 according to a further embodiment. The wire handling section of Fig. 4 includes a spool shaft 210 which is adapted to rotate a wire spool 212 about a spool axis 212a. The spool shaft 210 may be in accordance with any embodiment described herein, e.g. the spool shaft described in conjunction with Figs. 2a to 2c or Fig. 3. The spool shaft rotation may be driven by a spool motor. On the wire spool 212, wire 10 to be provided towards the wire web is carried in a wire carrying area 213a of the wire spool 212. The wire carrying area 213a has a wire carrying length along the direction of the spool axis, and is adapted for providing the wire 10 towards the wire web during unwinding of the wire from the spool. The spool shaft 210 is rotatably mounted to a main frame portion 100 of the wire saw device 1, and hence also the spool 212 is rotatably mounted in this manner. In contrast, the pulleys to be described below are generally freely rotatable.

[0029] A first pulley 220 is shown in Fig. 4. The first pulley 220 is adapted for receiving the wire 10 from the spool 212, and for then redirecting the wire. The first pulley is rotatably mounted to a pulley carrying unit 224, so that the first pulley 220 rotates about the first pulley axis 222. The pulley carrying unit 224, in turn, is connected to the wire saw device, more specifically to a main frame portion 100 of the wire saw device 1, so that the pulley 220 is longitudinally movable along a pulley motion track, i.e. the pulley motion track is defined as the region along which the pulley is movable. Further, the first pulley motion track may have a length of at least 90% of the length of a wire carrying area 213a of the spool 212. Here, the wire carrying area 213a is the lengthwise section of the spool 212 from which the wire may emerge from the spool, i.e. generally the length from flange to flange of the spool. As a further general aspect, the pulley motion track may extend over the length of the wire carrying area 213a, from flange to flange. The pulley motion track of the pulley 220 is essentially parallel to the spool axis 212a. Also, other directions of movement might be superimposed with the above described movement. For example, a curved track and/or an inclined track with respect to the spool axis 212a may be provided.

[0030] Further, a pulley moving device 228 is provided. The pulley moving device 228 is indicated by an arrow in Fig. 4, and is adapted to cause the pulley carrying unit 224 to move along the pulley motion track in a bi-directional mode. The pulley moving device 228 is adapted to move the pulley 220 and the wire position detection device along the motion track, (here: parallel to the axis 212a of the spool) in order to position the pulley at the desired position over the spool 212. According to various embodiments, which can be combined with other embodiments described herein, the pulley moving device 228 can be a linear actuator such as lineal motor, a pneumatic cylinder, a motor with a worm drive, a rack-pinion- gear or the like, such that the pulley moving device is capable of moving the pulley at least in a linear direction along the pulley motion track. Thereby, the pulley can be moved by moving the pulley carrying unit 224 relative to the main frame portion 100 of the wire saw device 1. [0031] Further, a wire position detection device 226 is provided. The wire position detection device detects the wire position along the direction of the motion path, or along the spool axis 212a, at which the wire traverses a detection region of the wire position detection device 226. Thereby, the position at which the wire 213a leaves the spool 212 or the wire carrying area 213a can be obtained (if necessary by triangulation).

[0032] Further, a controller is provided (not shown). The controller is operatively coupled to the wire position detection device 226 and to the pulley moving device 228. The controller has a winding mode and an unwinding mode. The unwinding mode is adapted for operation during which the wire 10 is unwound from the spool 212. In the unwinding mode, the controller receives the detected wire position from the wire position detection device 226. The controller then determines a target position for the first pulley, and transmits a moving command to the first pulley moving device 228, such as to cause the first pulley moving device 228 to move the first pulley 220 to the target position. In particular, the target position may be the position which corresponds to the position at which the wire 213a leaves the spool. Thereby, it is made sure that the wire always leaves the spool at a right angle with respect to the pulley axis 212a, as shown in Fig. 4. The first pulley moving device 228, the wire position detection device 226, and the first pulley position controller may be collectively referred to as a first pulley wire tracking system. Generally, a first pulley wire tracking system may be provided for allowing actuation of the first pulley moving device 228 in response to a detected wire position.

[0033] Further, as a general aspect the first pulley 220 is arranged such that for any position at which the wire 10 exits the wire carrying area 213a of coil 212, there is at least one position of the first pulley 220 on the pulley motion track such that the wire is entering the first pulley 220 essentially tangentially. Further, generally, the first pulley 220 (and any other pulleys if present in the embodiment, such as the second pulley 230 described below) is arranged such that for any position at which the wire 10 exits the wire carrying area 213a of coil 212, there is at least one position of the first pulley 220 on the pulley motion track such that the wire is exiting and entering any one of the coil and the pulleys essentially tangentially. This arrangement allows for a twist-free wire, which is defined as a situation in which the wire enters and exits any of the coil and the pulleys essentially tangentially. The controller may then be programmed to actuate, for any position of the wire 10 exiting the wire carrying area 213a, the pulley moving device 228 such that the wire is entering the first pulley 220 essentially tangentially. [0034] For the winding mode, the controller includes a wire winding pattern. In winding mode, the controller determines a desired wire winding position of the first pulley 220 for winding the wire 10 on the wire carrying area 213a of the spool, and transmits a moving command to the first pulley moving device 228 causing it to move the first pulley 220 to the desired wire winding position. Thus, the above-described combination of wire tracking system and controller allows bi-directional movement of the wire, i.e. a movement from the spool 212 to the wire web as well as a movement from the wire web to the spool 212.

[0035] The wire handling section of Fig. 4 further has a second pulley 230, which is adapted for receiving the wire from the first pulley 220, and for redirecting the wire. The second pulley 230 is rotatably mounted to the main frame portion 100 for rotation about a second pulley axis 232. Generally, within the wire handling section, further pulleys can be provided, and also a wire tensioner can be optionally provided (not shown). After being redirected by these pulleys, the wire 10 exits the wire handling section in direction of the wire web of the wire saw.

[0036] The expandable spool shaft as well as the winding and unwinding modes described above allow for a particularly useful sawing method, described below in conjunction with Figs. 5a to 5f. Here, reference signs given with respect to one figure also apply to corresponding parts given in the other figures unless specifically described otherwise.

[0037] Fig. 5a is a schematic side view of a wire saw device, more precisely of a wire management unit of the wire saw device. The wire management unit has a first wire handling section 200 including the shaft 210, here referred to as first shaft, and a first redirection system 202 for redirecting the wire from the spool to the wire web or vice versa. Generally, the first redirection system 202 includes a plurality of pulleys and optionally a wire tensioner. In particular, first redirection system 202 may include the pulleys shown in Fig. 4 above, or some of the pulleys and the wire tensioner shown in Fig. 6 below. Then, the shaft 210 and the first redirection system 202 may be arranged as described above in conjunction with Fig. 4 or as below in conjunction with Fig. 6. Also, a controller as described in conjunction with Fig. 4 may be provided. With this arrangement, Figs. 5a to 5f are views from the free end side of the spool shaft 210, such that the spool axis is perpendicular to the image plane.

[0038] The wire management unit of Fig. 5a further has a second wire handling section 300, including a second shaft 310 and a second redirection system 302. These elements are designed and arranged similarly to the first shaft 210 and the first redirection system 202, respectively, so that the second wire handling section 300 is generally in accordance with the description of the first wire handling section 200 above. The first and second wire handling sections are arranged with respect to each other such that the spool axes of the first spool shaft 210 and the second spool shaft 310 are parallel to each other and at the same height. In particular, the first and second wire handling section may be arranged as shown in Fig. 6. Further, the controllers of the first and the second wire handling section may be implemented as a single controller.

[0039] In Fig. 5a, no spools are mounted on the spool shafts 210 and 310. Now, with reference to Fig. 5b, a first wire spool 212 is mounted on a first spool shaft 210 of the wire saw device. The first wire spool is of a first type and carries wire saw wire 10. In particular, the first spool may be a spool from a wire supplier such as a TA100 spool. Also, if not already present from the beginning, a second spool 312 is mounted on the second spool shaft 310. The second wire spool is of a second type. In particular, the second spool may be a spool adapted for receiving wire to be wound on the second spool. The second spool may initially be empty. The different types of spools are indicated by the first spool 212 of first type being shaded, and by the second spool 312 of second type being non-shaded. The mounting of the first spool 212 on the first shaft 210 and / or the mounting of the second spool 312 on the second shaft 310 may be performed as described above, i.e. including the expansion of expandable surface portions of the respective shaft as shown e.g. in Figs. 2a to 2c.

[0040] Then, with reference to Fig. 5c, the wire 10 is unwound from the first wire spool 212 onto the second wire spool 312. Hereby, the wire goes through the first redirection system 202 to the wire web (to the right in Fig. 5c), and then coming from the wire web, it goes through the second redirection system 302. The direction of wire movement to / from the wire web is indicated by arrows on the line representing the wire 10. The redirection of the wire in the first and second redirection system 202, 302 is represented by dotted lines. This is only a schematic representation of the wire redirection, which may in actuality be more complex and involve more turns of the wire than the redirection shown in Fig. 5c (see e.g. Fig. 6 as an example). During the wire unwinding shown in Fig. 5c, the controller for the first spool shaft 210 may operate in unwinding mode, and the controller for the second spool shaft 310 (potentially being part the same controller as the controller for the first spool shaft) may operate in winding mode, as described above in conjunction with Fig. 4. Further, in Fig. 5c, sawing may optionally be carried out, such that a portion of the wire 10 forming the wire web may cut some material. [0041] When all the wire 10 has been unwound from the first wire spool 212, such that the first wire spool 212 is empty, the first wire spool 212 is unmounted from the spool shaft 210. The unmounting may also be performed as described above, i.e. including the retraction of expandable surface portions of the shaft 210. Then, another (third) wire spool 212 is mounted on the spool shaft 210. While the third spool 212 carries the same reference sign as the first spool, the third spool is of a second type, i.e. of the same type as the second spool 312, or of yet another type not being the first type. The mounting of the third spool 212 on the first shaft 210 may, again, be performed as described above, i.e. including expanding at least one expandable surface section of the spool shaft 210 essentially in a radial direction away from the spool axis, thereby tightening the third spool 212 on the spool shaft 210 such that the third spool 212 tightly fits on the spool shaft 210.

[0042] Then, with reference to Fig. 5e, the wire 10 is unwound from the second wire spool 312 onto the third wire spool 212. Hereby, the description of Fig. 5c applies also to Fig. 5e with the inverse wire direction, i.e. the wire going through the second redirection system 302 to the wire web, and then coming from the wire web through the first redirection system 202, as indicated by arrows on the line representing the wire 10. Thus, during the wire unwinding shown in Fig. 5e, the controller for the first spool shaft 210 may operate in winding mode, and the controller for the second spool shaft 310 may operate in unwinding mode, in analogy to the above description of Fig. 4. Further, in Fig. 5e, sawing may be carried out, i.e. a portion of the wire 10 forming the wire web may cut some material.

[0043] It can be appreciated that the wire saw device is ready for bi-directional sawing. Herein, bi-directional 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 bi-directional sawing the (primary) spool 212 is adapted for providing wire to the wire web and is also adapted for receiving used wire from the wire web. Likewise, the secondary spool 312 is adapted for providing wire to the wire web and is also adapted for receiving used wire from the wire web. According to the bi-directional sawing, after sawing as shown in Fig. 5e, the wire direction is inverted as shown in Fig. 5f, so that the wire is transported in the other direction than in Fig. 5e during sawing. In this manner, the sawing direction can be inverted periodically, switching from the direction shown in Fig. 5e to that in Fig. 5f and then switching back, and so forth. This bi-directional sawing is made possible by the wire spool shaft 210 being adapted for carrying a spool of a first type (as in Figs. 5b, 5c) and also a spool of a second type (as in Figs. 5d to 5f).

[0044] For the bi-directional 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.

[0045] Fig. 6 shows a perspective view of a wire management unit according to a further embodiment. The embodiment of Fig. 6 includes a first wire handling section 200, which will be described in the following. The first wire handling section 200 has the elements shown e.g. in Fig. 4, and the above description of Fig. 4 also applies to the first wire handling section 200 of Fig. 6. Further, a third pulley 240 is adapted for receiving the wire from the second pulley 230, in particular directly from the second pulley 230, and for redirecting the wire by a third redirection angle (here about 90°). The third pulley 240 is rotatably mounted to a main frame portion 100 for rotation about a third pulley axis 242. The third pulley axis 242 is essentially perpendicular to both the spool axis 212a and the second pulley axis 232.

[0046] Further, the first wire handling section 200 of Fig. 6 has a fourth pulley 250 receiving the wire from the third pulley and redirecting the wire by a fourth redirection angle. The fourth pulley 250 is rotatably mounted to the frame for rotation about a fourth pulley axis 252. Here, the fourth redirection angle is about 90° to 100°. In other embodiments, the fourth redirection angle may be between 60° and 120°. The fourth pulley axis 252 is essentially parallel to the spool axis 212a. Further, the fourth pulley axis 252 is essentially perpendicular to the first pulley axis 222, the second pulley axis 232, and the third pulley axis 242. In other embodiments, the fourth pulley axis 252 may be essentially parallel to at least one of these axes.

[0047] Further, in the embodiment of Fig. 6 the main frame portion 100 includes a mounting member 114, to which the second, third and fourth pulley 230, 240, 250 are mounted. The mounting member 114, 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. 6 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 100 (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 220 and the second pulley 230 (and, if present, 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.

[0048] The first wire handling section 200 of Fig. 6 further includes a wire tensioner for controlling the tension of the wire. The wire tensioner includes a fifth pulley 260 rotatably mounted to the frame for rotation about a fifth pulley axis 262 and a sixth pulley 270 rotatably mounted to a movable element 274 for rotation about a sixth pulley axis 272. The movable element 274 is movably mounted on the main frame portion. The movement of the movable element 274 may be controlled by a motor, or the movable element 274 may be pre-biased e.g. by a spring, for controlling the wire tension. In Fig. 6, the movable element 274 is shown as a pre-biased swivel lever. The wire tensioner receives the wire 10 from the fourth pulley 250 and provides the wire 10 to the wire web (to the right of the wire management unit shown in Fig. 6). More precisely, the fifth pulley 260 receives the wire 10 from the fourth pulley 250 and deflects the wire by a fifth deflection angle, and then the sixth pulley 260 receives the wire 10 from the fourth pulley 250 and deflects the wire by a sixth deflection angle.

[0049] In Fig. 6, in addition to the first wire handling section 200, there is also a second wire handling section 300. The second wire handling section 300 is constructed similarly to the first wire handling section 200 and has corresponding elements to the elements of the first wire handling section 200. The elements of the second wire handling section 300 are assigned reference signs 310, 312 etc. corresponding to the corresponding elements 210, 212 etc. of the first wire handling section 200. Thus, the second wire handling section 300 has e.g. a second spool shaft 310 for a second wire spool 312, etc. Generally, the second wire handling section 300 is formed in the same manner as the wire handling section 200 according to any embodiment described herein. The description of elements of the first wire handling section 200 is therefore also applicable to the corresponding elements of the second wire handling section 300. As a general aspect illustrated by, but independent of the shown embodiment, the first and the second wire handling sections 200, 300 may be placed on a common wall portion of the main frame portion 100. Further, the first and the second wire handling sections 200, 300 may be placed in a common compartment of the wire saw device.

[0050] In particular, the first spool shaft 210 and / or the second spool shaft 310 may be in accordance with any embodiment described herein, in particular with any of the embodiments shown in Figs. 2a to 2c and 3. Such a spool shaft design allows for operation of the first and second wire handling section 200, 300 as described in conjunction with in Figs. 5a to 5f. Here, the pulleys 220, 230, 240, 250, 260 and 270 of Fig. 6 correspond to the first redirection system 202 of Figs. 5a to 5f, and the pulleys 320, 330, 340, 350, 360 and 370 of Fig. 6 correspond to the second redirection system 302 of Figs. 5a to 5f.

[0051] According to different embodiments, the wire saw device described herein 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 spool shaft and the methods etc. described herein are particularly useful for the wire saw device being a squarer, but not limited to a squarer.

[0052] Further, the spool shaft might be particularly useful if thin wires or wires with a coating, e.g. a diamond coating, are used. Especially, the spool shaft is adapted for a squarer. 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 μιη, such as diameters between about 200 μιη and about 400 μιη, more particularly between about 200 μιη and about 300 μιη. However, in other cases embodiments may also have a wire diameter as low as 100 μιη or even 80 μιη, for example. 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 μιη to 340 μιη. Since mounting and unmounting of diamond wire may be necessary especially often, e.g. for bi-directional sawing or due to generally short wire length, the spool shaft disclosed herein is particularly useful for diamond wire.

[0053] In the following, some general aspects of the embodiments described herein will be summarized. Each of these general aspects or description of embodiments can be combined with any other general aspect(s), within any embodiment(s) described herein, to generate yet another embodiment or other embodiments.

[0054] According to an aspect, a wire saw device and/or portions thereof such as the wire handling portions, especially the pulleys, the wire spool shaft and/ or the wire spool, 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 of pulleys and guiding elements with an appropriate pitch of grooves, a different depth of grooves and/or a different shape of grooves than for conventional such elements. Thereby, 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.

[0055] According to a general aspect, a wire saw device further includes an expansion actuator operatively coupled to the at least one expandable surface section for actuating the expansion of the at least one expandable surface section away from the spool axis. The expansion actuator may include an external actuation input member at an axial free end of the spool shaft, the external actuation input member being adapted for receiving an actuation force actuating the expansion of the at least one expandable surface section away from the spool axis. In embodiments, the actuator is an element selected from the group consisting of a mechanical gear actuator; a hydraulic actuator; a pneumatic actuator; and an electric actuator. The external actuation input member may be rotatable about the spool axis, and by turning the external actuation input member in a first direction, the at least one expandable surface section may be expanded. Then, by turning the external actuation input member in a second direction, the at least one expandable surface section may be retracted towards the spool axis.

[0056] According to a general aspect, the at least one expandable surface section is a plurality of expandable surface sections. For example, at least 6 expandable surface sections may be provided. According to a further general aspect, the expandable surface sections may be arranged circumferentially around the spool axis in a regular spacing. In embodiments, the expandable surface sections are arranged in at least two rows, especially in staggered rows, i.e. the first row being staggered with respect to the second row. Further, in embodiments, the at least one expandable surface section are profiled, and may further include an elastic and / or high-friction material.

[0057] According to a further general aspect, the spool shaft has a spool carrying diameter of about 150 mm. Further, in embodiments the spool shaft is rotatably mounted to the main frame portion for rotation about a spool axis. Further, in embodiments the spool shaft has a free end for receiving the wire spool, and a stopper end for the wire spool.

[0058] According to a further general aspect, the spool shaft is adapted for carrying a spool of first type, and for carrying a spool of second type, the second type being different from the first type. According to embodiments, the spool of first type is adapted for providing the wire towards the wire web during unwinding of the wire from the spool, and the spool of second type is adapted for receiving the wire from the wire web during winding of the wire to the spool. In embodiments, the spool of first type is a TA100 spool.

[0059] According to a further general aspect, the spool shaft is a first spool shaft, and the wire saw device further includes a second spool shaft. The second shaft may have any features as described herein for the (first) shaft. Thus, the second shaft may be the same shaft type as the first shaft. The spool axis of the first shaft may be parallel to the spool axis of the second shaft. The first shaft and second shaft may be arranged in a common compartment of the wire saw device.

[0060] According to a further general aspect, the wire handling section further includes a bidirectional spool motor adapted for rotation in a first direction and in a second direction opposite to the first direction. According to a further general aspect, the wire saw device further includes a controller operatively coupled to the spool motor, the controller being operable in a winding mode and in an unwinding mode. In the unwinding mode, the controller causes the spool motor to rotate the spool shaft in the first direction so that the wire spool provides wire to the wire web for sawing, and in the winding mode the controller causes the spool motor to rotate the spool shaft in the second direction so that the wire spool receives wire from the wire web during sawing.

[0061] According to a further general aspect, the wire handling section is a first wire handling section, and the wire saw device further includes a second wire handling section including the second spool. Further, the first wire handling section may include a first wire tensioner and the second wire handling section may include a second wire tensioner. The first wire tensioner may be adapted to adjust the wire tension of the wire portion between the first spool and the wire web. The second wire tensioner may be adapted to adjust the wire tension of the wire portion between the second spool and the wire web. The first and second wire tensioner may be operatively coupled to a tension management unit of the wire saw device to respond to tensioning commands from the tension management unit.

[0062] According to a further general aspect, the controller is operatively coupled to a tension management unit for adapting rotation speed in response to a signal from the tension management unit. The program of the controller for the winding mode may be programmed such that for the tension to be increased, the controller causes the spool motor to increase the rotation speed of the spool shaft, and vice versa. The program of the controller for the unwinding mode may be programmed such that for the tension to be increased, the controller causes the spool motor to decrease the rotation speed, and vice versa.

[0063] According to a further general aspect, the 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 general 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 causing the first pulley moving device to move the first pulley to the target position. According to a further general aspect, the wire handling section is a first wire handling section, the wire management unit further including a second wire handling section. According to a further general aspect, the first wire handling section has a spool shaft that is adapted for carrying a spool of the first type, and the second wire handling section has a spool shaft that is adapted for carrying a spool of the second type.

[0064] According to a further general aspect, the spool has a wire carrying area, and the first pulley position controller for controlling the position of the first pulley 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 spool, and transmits a moving command to a first pulley moving device for causing the first pulley moving device to move the first pulley to the desired wire winding position.

[0065] According to a further general aspect, the wire saw device further includes a first pulley wire tracking system allowing actuation of the first pulley moving device in response to a detected wire position. According to a further general aspect, the first pulley wire tracking system includes: a first pulley moving device being e.g. 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 thereto causing the first pulley moving device to move the first pulley to the target position. [0066] According to a further general aspect, the wire saw device may further include a first pulley adapted for receiving the wire from the spool and for redirecting the wire. The first pulley may be e.g. rotatably mounted to a pulley carrying unit for rotation about a first pulley axis, the pulley carrying unit being longitudinally movable along a pulley motion track. According to a further general aspect, the wire saw device may further include a second pulley adapted for receiving the wire from the first pulley and for redirecting the wire, wherein the second pulley is rotatably mounted to the main frame portion for rotation about a second pulley axis. According to a further general aspect, the wire saw device may further include a third pulley adapted for receiving the wire from the second pulley and for redirecting the wire, wherein the third pulley is rotatably mounted to the frame for rotation about a third pulley axis. According to a further general aspect, the wire saw device may further include a fourth pulley adapted for receiving the wire from the third pulley and for redirecting the wire, wherein the fourth pulley is rotatably mounted to the main frame portion for rotation about a fourth pulley axis. Herein, a main frame portion is understood to be fixedly connected or connectable to the wire saw device chassis, so that e.g. a load can be absorbed by the chassis. The main frame portion may be one piece or multiple pieces. According to a further general aspect, a pulley motion track of the first pulley is arranged such that for any lengthwise position of the wire on the coil, there is a position of the first pulley on the pulley motion track such that the wire is fed to the first pulley twist-free. Here, the wire is defined to be twist-free when the wire is entering and exiting the pulleys tangentially. According to a further general aspect, the first and second pulley, and any other pulleys if present in the embodiment, are arranged such that for any lengthwise position of the wire exiting the coil, there is a position of the first pulley on the pulley motion track such that the wire is entering and exiting any one of the coils essentially tangentially.

[0067] According to a further general 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. According to a further general aspect, the wire saw device is adapted for a diamond wire, i.e. the wire includes a diamond coating. According to a general aspect, the wire saw device further includes a wire sawing region adapted for accommodating a wire web of the wire.

[0068] According to a further general aspect, a method of mounting a wire spool on a spool shaft of a wire saw device as described herein includes forming a wire web with the wire.

[0069] According to a further general aspect, a method of sawing using a wire saw device, in particular according to any other aspect or claim described herein, includes: - a first wire spool is mounted on a first wire spool shaft of the wire saw device, the first wire spool being of a first type and carrying wire saw wire; and optionally, a second wire spool is mounted on the second spool shaft. The second wire spool is of a second type. In particular, the second spool may be a spool adapted for receiving wire to be wound on the second spool. The mounting of the first and / or second spool on the respective shaft may include the expansion of expandable surface portions of the respective shaft, and especially the mounting method described above may be used.

- the wire is unwound from the first wire spool onto the second wire spool. During the wire unwinding, a controller may operate in unwinding mode for the first spool shaft, and may operate in winding mode for the second spool shaft. Optionally, sawing may be carried out, i.e. the portion of the wire in the wire web may cut some material;

- the first wire spool is unmounted from the first spool shaft. The unmounting may include the retraction of expandable surface portions of the shaft;

- a third wire spool is mounted on the first wire spool shaft, the third spool being e.g. a second type spool; and

- bi-directional sawing is carried out by the wire. During bi-directional sawing, the wire alternates between the second spool and the third spool. Further, during bi-directional sawing, a first sawing direction and a second sawing direction are periodically interchanged. During sawing in the first sawing direction, the wire is unwound from the second wire spool onto the third wire spool. Here, the controller may operate in winding mode for the first spool shaft, and in unwinding mode for the second spool shaft. During sawing in the second sawing direction, the wire direction is inverted with respect to the first sawing direction. For bidirectional sawing, the sawing direction can be inverted periodically, switching from the first direction to the second direction and back periodically.

[0070] According to a further general aspect, a wire saw device, in particular one according to any claim or general aspect or embodiment described herein, is adapted for accommodating a wire forming a wire web for cutting, the wire saw device having a first spool shaft adapted for carrying a wire spool and a second spool shaft adapted for carrying a second wire spool, and a controller containing program code adapted for controlling the wire saw to perform the method steps as described above. [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.