The invention relates to a wire saw for cutting a piece of material, particularly for slicing, squaring and/or bricking a piece of semiconductor material, comprising a first compartment in which wire guide rollers for supporting a cutting field formed from a cutting wire are arranged.

JPH07153724A discloses a wire saw for slicing silicon ingots. The wire saw comprises wire guide rollers supporting a wire web and spools for supplying cutting wire to the wire web and for taking-up cutting wire from the wire web. A housing cassette is provided with grooves for accommodating the silicon wafers WO2013018556A1 discloses a wire saw comprising wire guide rollers across which the cutting wire is suspended in multiple loops. Bobbins are provided on the supply side and winding side of the wire web. Sensors are provided to measure the tension of cutting wire between the wire guide rollers and the bobbins.

JP H06 52151 U and JP H06 334039 A discloses saws of different type without cutting field. On both sides of the cutting compartments lateral compartments are provided for accommodation storage spools. The wire extends from one of the lateral compartments through the cutting compartments to the other lateral compartment.

JP H07 314436 A discloses a wire saw having a cutting field supported by wire guide rollers. Lateral compartments accommodate storage spools. The openings between the compartments for feeding through the cutting wire do not protect the lateral compartments from cutting liquid, dirt and material particles.

JP 2006 192539 A discloses a wire saw comprising a cutting field supported by wire guide rollers. Disadvantages in prior art occur due to the fact that the cutting area (comprising the wire guide rollers and the wire web) is not sufficiently separated from the area in which the pulleys and/or spools for (temporarily) storing cutting wire are arranged. Cutting liquid, dirt and material particles have an adverse impact on spools, and the wire thereon, deflection pulleys and tension means. Cleaning and maintenance of wire saws are time wasting and expensive procedures. Moreover, damages at the force measuring system and the pulley bearing may occur. A further disadvantage in prior art is the poor accessibility to parts of the wire saw, particularly to the cutting wire path, to the storage spools and deflection pulleys.

The object of the invention is to overcome these problems and to provide a wire saw in which a significant portion of the cutting wire that is not part of the cutting field as well as pulleys and/or spools for guiding and/or storing the cutting wire are efficiently protected from the adverse effects of cutting liquid, dirt and material particles. At the same time it should be possible to realize functionalities known from wire saws according to prior art. Particularly, the position of the cutting field on the wire guide rollers (i.e. the position along the axes of the wire guide rollers) and the width of the cutting field (i.e. the number of loops) should be variable.

In an preferred aspect of the invention accessibility should be increased. Particularly, the wire saw should allow for optimal accessibility to its parts, particularly to the cutting wire path extending between the wire web (i.e. cutting field) and a storage spool. The object is achieved by a wire saw as mentioned at the beginning in that the wire saw comprises

at least one second compartment for accommodating a portion of the cutting wire,

an opening connecting the first compartment with the second compartment, - screening means for preventing ingress of cutting liquid, dirt and/or material particles through the opening into the second compartment,

at least one cutting wire feedthrough for guiding the cutting wire from the first compartment through the screening means towards the second compartment, wherein preferably the cutting wire feedthrough extends through the opening. The second compartment which is separated from the first compartment allows to accommodate a portion of the cutting wire, preferably also (deflection and/or tension) pulleys and/or spools for storing cutting wire. The cutting wire coming from the cutting field extends through the opening and runs and/or is (temporarily) stored within the second compartment. Cutting wire and wire guiding, wire tensioning and/or wire storing means (such as pulleys, spool, etc.) are protected within the second compartment. Additionally, the screening means prevents cutting liquid, dirt and/or material particles located in the cutting area (first compartment) from ingressing into the second compartment. The cutting wire feedthrough extends through the screening means and protects the cutting wire when passing from the first compartment to the second compartment. The screening means may be arranged outside the opening (thereby covering the opening) and/or within the opening. In the first case the feedthrough may extend only through the screening means, however, it is preferred that the feedthrough extends also through the opening, in order to prevent the cutting wire from damage. The opening may be provided in a wall separating the second compartment from the first compartment.

Screening means may comprise several portions or elements and may protect the opening in several stages. For example: screening means may have at least two covers, wherein the upper cover (e.g. a rigid shield) at least partially covers a lower cover (e.g. flexible sealing lips). Additional lateral covers screening, at least partially, other parts of the screening means are also possible.

Preferably, the wire saw comprises two second compartments each for accommodating a portion of the cutting wire. Each second compartment is connected with the first compartment by an opening which is provided with screening means for preventing ingress of cutting liquid through the opening. Cutting wire feedthroughs guide the cutting wire from the first compartment through each screening means. It is preferred if the opening towards one of the second compartments is arranged on one side of the cutting field and the opening towards the other second compartment is arranged on the other (opposing) side of the cutting field. One opening towards one of the second compartments may be stationary.

The opening is preferably provided in a wall portion separating the first compartment from the second compartment(s).

It is preferred, if the second compartment(s) is/are arranged directly adjacent to the first compartment. The compartments may be separated from each other e.g. by a wall.

Preferably, the second compartment(s) is/are arranged below, preferably directly below, the first compartment. The advantage of this embodiment is that the wire saw can be designed very compact and place-saving, if a portion of the cutting wire (coming from the cutting field and running to a spool for storing, at least temporarily, cutting wire) is arranged below the first compartment. The first compartment includes the cutting area, i.e. the area in which the wire guide rollers and the cutting field are arranged.

The object is also achieved by means of a wire saw for cutting a piece of material, particularly for slicing, squaring and/or bricking a piece of semiconductor material, particularly according to the foregoing embodiment(s), comprising

a first compartment in which wire guide rollers for supporting a cutting field formed from a cutting wire are arranged,

at least one second compartment for accommodating a portion of the cutting wire,

- an opening connecting the first compartment with the second compartment and for feeding through cutting wire,

wherein the opening is formed between a first edge and a second edge, wherein the first edge is moveable relative to the second edge, such that the distance between the first edge and the second edge may be changed,

- wherein preferably in a first (closed) position the first edge at least partially abuts against the second edge and in a second (opened) position the first edge is distanced from the second edge.

The first edge may be moved away from the second edge. In such a way direct access is provided to the cutting wire portion extending through the opening between the first compartment and the second compartment. This allows e.g. for simple exchange of cutting wire. The edge may be e.g. straight or curved.

Also in the first position an opening for the cutting wire is kept free. However, next to the opening the edges may at least partially abut against each other, in order to form a sealed arrangement. Preferably, the first edge is formed on a cover moveable between a closed state and an opened state, wherein preferably the cover at least partially covers the first compartment in the closed state and allows access to the first compartment in the opened state. The cover is part of the housing of the wire saw. The cover may be e.g. a slidable cover, a hinged cover (e.g. in form of a door), a flexible cover or a (roller) shutter.

Preferably, the first edge and the second edge extend along, preferably essentially parallel to, the rotational axes of the wire guide rollers. Here, the position, where the cutting wire is fed through, may be changed (see also: embodiments having a moveable cutting wire feedthrough)

Preferably, the wire saw comprises screening means for preventing ingress of cutting liquid, dirt and/or material particles through the opening into the second compartment, wherein at least a portion of screening means is formed on the first edge and/or on the second edge.

Preferably, screening means comprises a longitudinal sealing lip, preferably formed from flexible material, formed on the first edge and/or a longitudinal sealing lip, preferably formed from flexible material, formed on the second edge. Preferably, the wire saw comprises at least one cutting wire feedthrough for guiding the cutting wire from the first compartment through the opening towards the second compartment, wherein the longitudinal sealing lip(s) abut(s) against the feedthrough preferably from opposing sides.

In a preferred embodiment the feed-through direction defined by the cutting wire feedthrough is tangential to the surface of one of the wire guide rollers. In this embodiment it is not necessary to provide any deflection pulleys within the first compartment (arrangement of pulleys within the cutting area would be disadvantageous due to cutting fluid and dirt). The cutting wire leaves a wire guiding roller (tangentially) and directly runs towards the feed-through. The feed- through direction is that direction, in which the cutting wire extends when passing the feedthrough. In the case of a cylindrical feedthrough (e.g. a tube) the feed- through direction will coincide with or be essentially parallel to the cylindrical axis.

In a preferred embodiment the cutting wire feedthrough is moveable along a direction essentially parallel to the axes of the wire guide rollers, preferably by at least 5cm, more preferred by at least 10 cm. The wire saw becomes more flexible since it becomes possible to vary the position and/or width of the cutting field along the axes of the wire guide rollers. Particularly, the (axial) position of the cutting wire section leaving the wire guide rollers towards a feedthrough may be adjusted. This is done by moving the feedthrough to the corresponding position and winding the wire guide rollers in an appropriate way. At the same time the screening means efficiently prevents cutting liquid from passing the opening. In an preferred embodiment the feedthrough is moveable along at least 50%, preferably along at least 80%, of the length of the wire guide rollers. The moveable feedthrough may be supported by a guide (e.g. a rail) or coupled to a wire (deflection) pulley which is arranged in the second compartment. It is preferred if the moveable feedthrough may be fixed at a certain position along the axis direction of the wire guide rollers. Fixing means may be e.g. screws, breaks, etc.

In a preferred embodiment at least a portion of the screening means is coupled to and/or cooperates with the cutting wire feedthrough thereby adapting its shape and/or position in dependence of the position of the cutting wire feedthrough. The screening means may be adaptable (in shape and/or position) such that the screening functionality is ensured independently of the position of the feedthrough. For example: At least a portion of the screening means (e.g. a shield) may be directly attached to or formed with the feedthrough. Or: At least a portion of the screening means may be flexible; it will change its shape in the vicinity of the feedthrough (e.g. snuggle against the feedthrough), thereby minimizing leakage. In a preferred embodiment at least a portion of the screening means is made of a flexible material, preferably of rubber, wherein preferably the flexible material abuts against the cutting wire feedthrough and the cutting wire feedthrough is moveable relative to the flexible material. The flexible material may at least partially surround the feedthrough thereby providing an efficient sealing also in the immediate vicinity of the feedthrough. The flexible material is elastic: When moving the feedthrough (e.g. in axial direction of the wire guide rollers) the flexible material will adapt its shape according to the position of the feedthrough.

In a preferred embodiment the screening means comprises at least one, preferably at least two longitudinal sealing lip(s) abutting against the feedthrough preferably from opposing sides. The sealing lip(s) may be stationary with respect to the opening (i.e. opening between first and second compartment), while the feedthrough is moveable along the longitudinal direction of the sealing lip(s).

In a preferred embodiment the screening means comprises a shield mounted to the feedthrough, wherein preferably the shield covers the opening (completely or partially), wherein preferably the shield extends, in at least one direction, beyond the opening. In the case of additional screening components (e.g. sealing lips) the shield may extend beyond the opening by at least 4mm (e.g. between 5mm and 15mm). Otherwise (or alternatively) the shield may preferably extend beyond the opening by at least 5cm, preferably by at least 10cm. In the case of a moveable feedthrough the shield is automatically moved with the feedthrough thereby optimally screening the opening independent of the position of the feedthrough. The shield may extend - at least in one position of the feedthrough - beyond the opening. In such an overlapping arrangement the screening efficiency is improved. An overlapping arrangement also allows movement of the feedthrough without giving access to the opening in any position of the feedthrough.

In a preferred embodiment the screening means comprises at least one, preferably at least two, portion(s) of variable in length, wherein preferably the cutting wire feedthrough is arranged between two portions of variable length. The portion(s) of variable length (with other words: cover of variable length) will change its/their length(s) when moving the feedthrough thereby covering the opening independent of the position of the feedthrough. For example: The at least one feedthrough may be formed or arranged on a moveable slide that is connected on both sides with a portion of variable length. In a preferred embodiment the at least one portion of variable length is formed by a bellow and/or by telescopic screening elements.

In a preferred embodiment the wire saw comprises a deflection pulley which is arranged in the second compartment and deflects the cutting wire coming from the cutting wire feedthrough. This allows e.g. place-saving design, tensioning the cutting wire and placing it on a storage or working spool.

In a preferred embodiment the deflection pulley is moveable along a direction essentially parallel to the axes of the wire guiding rollers, wherein preferably the cutting wire feedthrough is coupled to the deflection pulley. The movement of the pulley and the feedthrough is synchronized allowing simple adjustment of the cutting field (position and/or width).

In a preferred embodiment the opening is formed as a slit extending essentially parallel to the axes of the wire guide rollers.

In a preferred embodiment the cutting wire feedthrough is formed by a duct, preferably a straight duct, preferably in form of a tube. The tube may have a closed mantle or have a slit along its longitudinal extension (e.g. jacket- or sleeve-like). Longitudinal profiles, such as U-profiles or flat profiles, at least partially surrounding the cutting wire, may be used as well. In a preferred embodiment the wire saw comprises at least one cutting wire spool for storing, at least temporarily, cutting wire coming from the cutting wire feedthrough in multiple loops, wherein the cutting wire spool is arranged in the second compartment. Preferably, the wire saw comprises at least one cutting wire spool for storing, at least temporarily, cutting wire coming from the cutting wire feedthrough in multiple loops, wherein the cutting wire spool is arranged below, preferably directly below, the first compartment. In such a way a space-saving design is achieved.

In a preferred embodiment in the second compartment a collecting reservoir is provided for collecting cutting liquid, wherein preferably the collecting reservoir is provided with a discharge. Screening means minimizes leakage of the transition between first and second compartment. In the case an minor amount of cutting liquid passes the barrier it will be collected in a defined space and may be removed from there e.g. by a discharge channel. Preferably, the wire saw is a wafer cutting wire saw for cutting a plurality of wafers from the piece of material and/or wherein the cutting field is formed from a plurality of cutting wire loops running around the wire guide rollers.

Further embodiments of the invention are indicated in the figures and in the dependent claims. The list of reference marks forms part of the disclosure. The invention will now be explained in detail by the drawings. In the drawings:

Fig. 1 shows a wire saw according to the invention,

Fig.2 shows a preferred embodiment of a wire saw with screening means in form of a shield and sealing lips,

Fig 3 the run of the cutting wire from the cutting field (first compartment) to the spool (second compartment),

Fig 4 a detail of the wire saw of Fig.2,

Fig 5 the cutting wire feedthrough of Fig. 4 with shield and mounting structure,

Fig 6 an embodiment of the screening means in form of telescopic elements, Fig. 7 an embodiment of the screening means in form of bellows,

Fig. 8 two possible cutting field arrangements

Fig. 9 an embodiment of the invention with an openable cover.

Fig. 1 shows a wire saw 10 for cutting a piece of material, particularly for slicing, squaring and/or bricking a piece of semiconductor material. Wire saw 10 comprises a first compartment 1 in which wire guide rollers 3, 4 for supporting a cutting field 5 formed from a cutting wire 6 are arranged and second compartments 2 each for accommodating a portion of the cutting wire 6.

As can be seen from Fig. 3 and 8 the wire saw 10 may be a wafer cutting wire saw for cutting a plurality of wafers from the piece of material (e.g. semiconductor material, such as silicon). The cutting field 5 is formed from a plurality of cutting wire loops running around the wire guide rollers 3, 4.

An opening 7 connects the first compartment 1 with a second compartment 2. The cutting wire 6 extends from the first compartment 1 through the opening 7 to the second compartment 2.

Screening means 11, 12 partially cover the opening 7 and prevent ingress of cutting liquid, dirt and/or material particles through the opening 7 into the second compartment 2. A cutting wire feedthrough 8 guides the cutting wire 6 from the first compartment 1 through the screening means 11, 12 towards the second compartment 2. In the embodiment shown the cutting wire feedthrough 8 extends also through the opening 7. The cutting wire feedthrough 8 may be formed by a tube, preferably a straight tube (e.g. Fig. 5).

As can be seen from the embodiment of Fig. 1, the feed-through direction defined by the cutting wire feedthrough 8 is tangential to the surface of the corresponding wire guide roller 3, 4.

A deflection pulley 9 is arranged in the second compartment 2 (in the vicinity of opening 7) and deflects the cutting wire 6 coming from the cutting wire feedthrough 8. The wire saw 10 also comprises in each second compartment 2 a cutting wire spool 15 for storing, at least temporarily, cutting wire 6 in multiple loops. As can be seen from Figs. 1 and 3 the cutting wire spools 15 are arranged directly below, the first compartment 1.

As indicated in Figs. 3, 4, 6, 7 and 8 (double arrow) the cutting wire feedthrough 8 is moveable along a direction essentially parallel to the rotational axes of the wire guide rollers 3, 4, preferably by at least 5cm, more preferred by at least 10 cm. The opening 7 may be formed as a slit extending essentially parallel to the axes of the wire guide rollers 3, 4.

The deflection pulley 9 is also moveable along a direction essentially parallel to the axes of the wire guiding rollers 3, 4. In the present embodiment the cutting wire feedthrough 8 is coupled to the deflection pulley 9 for synchronized movement. Fig. 5 shows an embodiment of a feedthrough 8 having a mounting structure 17 for coupling with the pulley 9 (or its support).

At least a portion of the screening means is coupled to and/or cooperates with the cutting wire feedthrough 8 thereby adapting its shape and/or position in dependence of the position of the cutting wire feedthrough 8.

In the embodiments of Figs. 1 , 2 and 4 at least a portion of the screening means 11 is made of a flexible material, preferably of rubber. The flexible material abuts against the cutting wire feedthrough 8 and the cutting wire feedthrough 8 is moveable relative to the flexible material. In the present embodiment the screening means comprises two longitudinal sealing lips 11 abutting against the feedthrough 8 from opposing sides (Fig. 4) - or against each other in areas where the feedthrough 8 is not present.

The screening means further comprises a shield 12 mounted to the feedthrough 8. It is preferred that the shield 12 (at least partially) covers the opening 7 and extends, in at least one direction, next to the feedthrough 8, preferably by at least 5cm, more preferred by at least 10cm.

In an alternate embodiment (not shown) it may be preferred that the shield 12 covers the complete opening 7 and extends, in at least one direction, beyond the opening 7 by at least 4mm, more preferred by at least 5cm, even more preferred by at least 10cm .

In the embodiments of Figs 6 and 7 the screening means comprises portions of variable in length. The at least one (here: two) cutting wire feedthrough 8 may be arranged (e.g. on a slide) between two portions of variable length. The at least one portion of variable length may be formed by a bellow 13 (Fig. 7) and/or by telescopic screening elements 14 (Fig. 6).

It is preferred that in the second compartment 2 a collecting reservoir 16 is provided for collecting cutting liquid (Fig. 1 and 7). The collecting reservoir 16 may be provided with a discharge.

Fig. 8 shows the principle of the embodiment, in which the feedthrough 8 is moveable along the axes of the wire guide rollers 3, 4. By positioning the feedthroughs 8 different cutting fields 5 may be realized: they may e.g. vary in position and or width. The screening means 11, 12, 13, 14 ensure efficient screening independent of the position of the feedthroughs 8 and thus independent of current cutting field dimensions.

Fig. 9 shows a preferred aspect of the present invention, which may be realized in combination, but also independent of the foregoing embodiments.

Fig. 9 shows a detail of a wire saw 10 comprising a first compartment 1 in which wire guide rollers 3, 4 for supporting a cutting field 5 formed from a cutting wire 6 are arranged (see Fig. 1), a second compartment 2 for accommodating a portion of the cutting wire 6 and an opening 7 connecting the first compartment 1 with the second compartment 2 for feeding through cutting wire 6. The opening 7 is formed between a first edge 18 and a second edge 19, wherein the first edge 18 is moveable relative to the second edge 19, such that the distance between the first edge 18 and the second edge 19 may be changed.

In a first position the first edge 18 abuts at least partially against the second edge 19 (but still keeping an opening 7 for the cutting wire 6 or the cutting wire feedthrough 8, respectively) and in a second position the first edge 18 is distanced from the second edge 19.

In the present embodiment the first edge 18 is formed on a cover 20 moveable between a closed state (full lines) and an opened state (dashed lines). The cover 20 at least partially covers the first compartment 1 in the closed state and allows access to the first compartment 1 in the opened state. The first edge 18 and the second edge 19 extend along, preferably essentially parallel to, the rotational axes of the wire guide rollers 3, 4 (i.e. here: perpendicular to the plane of Fig. 9' drawing). Screening means 11 are formed on the first edge 18 and on the second edge 19. Here, screening means 11 comprises a longitudinal sealing lip, preferably formed from flexible material, formed on the first edge 18 and/or a longitudinal sealing lip, preferably formed from flexible material, formed on the second edge 19 (compare with Fig.4).

The longitudinal sealing lips 11 abut against the feedthrough 8 preferably from opposing sides (see also Fig.4).

The invention is not restricted to these embodiments. Other variants will be obvious for the person skilled in the art and are considered to lie within the scope of the invention as formulated in the following claims. Individual features described in above specification, particularly with respect to the figures may be combined with each other to form other embodiments and/or applied mutatis mutandis to what is described in the claims and to the rest of the description.

List of reference signs

1 first compartment

2 second compartment

3 wire guide roller

4 wire guide roller

5 cutting field

6 cutting wire

7 opening

8 cutting wire feedthrough

9 pulley

10 wire saw

11 sealing lip

12 shield

13 bellow

14 telescopic element

15 spool

16 collecting reservoir

17 mounting structure

18 first edge

19 second edge

20 cover