EP1437209B1 - Wire sawing device - Google Patents

Abstract

The device has a wire strand maintained in position by a groove provided on a surface of cylindrical guides. Wires move alternately or continuously to press against a fixed saw piece (17) on a support table (18). A maintaining device (22) maintains partially or fully sawed chips (23) in parallel. The device is arranged such that widths of sawing gaps (24) are kept approximately constant during sawing of chips by wire.

Description

The present invention relates to a wire sawing device according to the preamble of claim 1.

such a device is described by JP 9 272 122 A.

Thread sawing devices of the aforementioned type with displacement of the yarns of the sheet of yarn or of the part to be sawn are already known, especially in the industry of electronic components of ferrites, quartz and silicas, for slicing. fine materials such as poly- or monocrystalline silicon or new materials such as GaAs, InP, GGG or also quartz, synthetic sapphire, ceramic materials. The high price of these materials makes wire sawing more attractive compared to other techniques such as diamond sawing.

In known devices, the sawing zone consists of a set of at least two cylinders placed in parallel. These cylinders, called son-guides, are engraved with grooves defining the interval between the threads of the web, ie the thickness of the slices. The piece to be sawn is fixed on a support table which moves perpendicularly to the sheet of threads. The speed of movement defines the cutting speed. The renewal of the yarn and the control of its tension is done in a part called yarn management area located outside the actual sawing area. The agent that will govern the cutting is either an abrasive attached to the wire, or a free abrasive brought as a slurry. The wire only acts as a carrier. When cutting in thin slices of the workpiece, the tensioned wire is both guided and pulled by the wire guide cylinders.

For many applications, sawn slices or wafers are very thin relative to the diameter of the workpiece. The sawn slices thus have considerable flexibility and can flex and bend to contact adjacent slices. These deflections are detrimental to the precision and flatness of the cut and can induce undesirable corrugations, streaks and irregularities on the surface of sawn slices. These irregularities, even a few micrometers are enough to make unusable slices for certain applications, such as silicon for the solar industry and semiconductors. The deformations of the slices can even induce microcassures and breaks, especially near the fixing of the slices to their support.

In addition, variations in the position of the slices and in the width of the sawing gaps are likely to influence the supply and distribution of free abrasive in the interstices of sawnwood, which in turn causes variations in the slice thickness, sawing speed and yarn wear, thus a further increase in the irregularities of the surface of the slices obtained, as well as an increased risk of wire breakage.

If the wire breaks, it is very difficult, if not impossible, to repair the wire and to make it penetrate again between slices that touch or whose sawing gap has become very small. It is then necessary to discard the workpiece in case of breakage of the wire and start sawing again with a new part, which causes a considerable loss of materials often very expensive and sawing time.

JP 9272122 A and its English abstract disclose a sawing device of the aforementioned type which comprises a pressure plate mounted on a support plate which can be moved vertically by means of a jack actuation mechanism. A workpiece is cut an initial distance by a sheet of son and then brought into contact with the pressure plate which is pressed against the workpiece during sawing to prevent the appearance of cracks on sawn slices.

The present invention aims to obtain a sawing device to further increase the quality and operation of the sawing and the sawing device according to the invention comprises for this purpose the features of the independent claim.

Thanks to these characteristics, it is possible to obtain very flat slices, without undesirable undulations, striations and irregularities. Microcures and breaks are completely avoided.

Because the sawing gaps are maintained at a constant width, a supply and distribution of regular free abrasive is obtained, thus regular sawing without corrugations and at a constant speed from one sawing slot to the next.

The wire is also used regularly, so it is less subject to breakage. In case a break should occur, the device according to the invention can also contribute to easy repair of the wire and a replacement of the wire in the sawing gaps, thus to avoid the rejection of the workpiece following a break in the thread.

Thanks to the claimed characteristics, the holding device allows a particularly efficient and reliable operation and a simple and inexpensive construction.

According to another embodiment, the holding members comprise a thick liquid or a gel of a higher density than the machining liquid used, the thick liquid or the gel being contained in a tank maintained in the active position of such that said portion of the slices is at least partially immersed in the thick liquid or gel so that the slices are immobilized.

These features of the holding device make it possible to obtain an original and inexpensive solution for overcoming the disadvantages of the aforementioned corrugations and surface irregularities.

As a variant, the holding device can also comprise, as holding members, separating elements intended to be introduced at least partially into the sawing gaps between the slices in order to maintain the latter, these separating elements being mounted on at least a support.

Thanks to these characteristics, the gap between the slices can be kept constant very precisely, even in the event of external forces acting on the slices being sawn.

Favorably, the separation elements are constituted by son, strips, blades or walls of a suitable thickness to be introduced into said sawing gaps.

Maintaining and separating the sawn slices are thus made simply and efficiently.

According to an advantageous embodiment, said at least one support is arranged in at least one tray mounted on said frame.

These features allow easy integration of sawn slices into a production line.

Other advantages emerge from the features expressed in the dependent claims and from the following description explaining the invention in more detail with the aid of drawings which show schematically and by way of example several embodiments and variants.

• La figure 2 est une vue partielle agrandie de face de ce premier mode d'exécution.
• La figure 3 est une vue de côté du dispositif de maintien de la figure 2.
• La figure 4 est une vue partielle de face d'un second mode d'exécution.
• Les figures 5 et 6 représentent un troisième mode d'exécution en vue de face partielle et en perspective partielle.
• La figure 7 est une vue partielle de face d'une variante combinant les premier et troisième modes d'exécution.
• Les figures 8 et 9 illustrent un quatrième mode d'exécution en perspective et en vue partielle de face.
• Les figures 10 à 13 représentent un cinquième mode d'exécution en perspective, en vue de côté, en vue de face au début et à la fin du sciage.
• La figure 14 montre une variante du mode d'exécution précédent.

Figure 1 is a front view of a first embodiment of the invention.

• Figure 2 is an enlarged partial front view of this first embodiment.
• Figure 3 is a side view of the holding device of Figure 2.
• Figure 4 is a partial front view of a second embodiment.
• Figures 5 and 6 show a third embodiment in partial front view and in partial perspective.
• Figure 7 is a partial front view of a variant combining the first and third embodiments.
• Figures 8 and 9 illustrate a fourth embodiment in perspective and partial front view.
• Figures 10 to 13 show a fifth embodiment in perspective, in side view, in front view at the beginning and at the end of the sawing.
• Figure 14 shows a variant of the previous embodiment.

With reference to FIGS. 1 to 3, the sawing device according to the first embodiment comprises a frame 10 and wire guide cylinders 11, 12, here two in number, mounted on this frame with their axes arranged in parallel, being of course that the device could have more than two cylinders guide son.

The yarn 14 is unwound from a delivery reel, not shown, and then wound around the yarn guide rolls in any possible winding mode to form at least one web of parallel yarns in a sawing zone. The yarn is then recovered in a suitable device, not illustrated, such as a take-up reel or a recovery tank.

One, two or more workpieces 17, such as ingots of hard material, are mounted on a support table 18 via a temporary support 19.

This support table 18 can be moved vertically in the Z direction by a column 21 and a motor 20 to support the workpieces 17 against the sheet of son 15.

The periphery of the wire guide rolls 11, 12 is etched with grooves which define the gap between the adjacent son of the son sheet 15, thus the thickness of the sawn slices. These are separated from each other by slots or sawing gaps.

The wire 14 is stretched and both guided and pulled by the wire guide cylinders to reciprocate reciprocally or continuously. This wire is favorably constituted of spring steel with a diameter of between 0.1 and 0.2 mm in order to saw blocks of hard materials or of a more particular composition, such as silicon, ceramic, compounds of the elements of groups III -V and II-VI, GGG (Gadolinium-Gallium Garnet), sapphire, etc., in slices of about 0.1 to 5 mm thick. The abrasive agent is a commercial product and can be diamond, silicon carbide, alumina, etc., in a form fixed to the wire or in free form suspended in a liquid which serves as a carrier for the particles of the 'abrasive.

The sawing device is, according to the invention, provided with a holding device 22 arranged so as to maintain, during sawing, the slices 23 partially or entirely sawn apart substantially parallel to each other and so that the width gaps of sawn timber 24 is kept substantially constant during the sawing of the slices.

The holding device 22 comprises for this purpose holding members 25 capable of cooperating with at least a portion 26 of the slices being sawed. This portion 26 is here opposite the portion 27 of the workpiece 17 by which the latter is fixed to the support table 18.

These holding members 25 comprise, in the embodiment of FIGS. 1 to 3, a longitudinal bar 30 per sawing pieces extending along the latter in a direction substantially perpendicular to the son of the ply of threads 15. The bars 30 are provided with coatings 31 made of elastomer to be applied against the edges of the workpieces.

Each bar 30 is pivotally mounted along a pivot axis 32 parallel to the wire guide cylinders 11, 12 on crosspieces 33. Thus, the coatings 31 can optimally adapt to the workpiece 17. The cross members 33 slide on rods 34 acting as guiding elements integral with the support table 18. Elastic means in the form of coil springs 35 urge the crosspieces 33 and the longitudinal bars 30 towards the part of the parts to be sawed 17 and other part of stationary stops 40 integral with the frame 10.

When the workpieces are in a position spaced apart from the ply of threads 15, the crosspieces 33 rest on the stationary abutments 40, and the holding members 25 are in this inactive position spaced apart from the workpieces 17.

These sawing pieces 17 are for sawing lowered to come into contact with the ply of threads 15. After sawing a minimum distance of, for example, one centimeter, the elastomer coatings 31 come into contact with the workpieces to be cut. and maintain in this active position the slices sawn firmly in place by the action of the springs 35, the stationary stops 40 then being separated from the crosspieces 33. Adjusting screws 41 provided on these stationary stops 40 make it possible to determine exactly the position in which, the holding members 25 come into action.

The sawing can then continue to the opposite end of the workpiece, while the sawn slices 23 are held in position, to avoid undulations, striations and other irregularities due to transverse displacements of the slices. The slots or sawing gaps 24 have a constant width allowing a regular supply of abrasive particles and a constant sawing speed.

The embodiment shown in Figure 4 is similar to that of Figures 1 to 3, except that the holding device 22 is of a different type. Indeed, the holding members 25 comprise in this case a thick liquid or a gel 45 higher density than the machining fluid used. This thick liquid or gel is contained in a tank 46 which is fixed on the sleepers 33 mounted sliding on the rods 34. It may for example be used silicones of adequate viscosity.

The crosspieces 33 are subjected to the action of the coil springs 35 and locked in the active position by locking washers 47 so that the lower portion 26 of the slices is at least partially immersed in the thick liquid or the gel which penetrates partially in the sawing gaps 24 and thus immobilizes the slices sawed in parallel position.

A third embodiment illustrated in FIGS. 5 and 6 comprises as holding member 25 separating elements intended to be introduced at least partially into the interstices 24 between the slices 23 to hold the latter. In the illustrated mode, a series of son 50 is stretched on a frame 51 and arranged parallel to the son of the sheet of son 15. In active position, these son 50 are introduced into the sawing gaps 24 between the slices 23 to maintain exactly the gap between them. The frame 51 cooperates in an inactive position with the stationary stops 40 to separate the wires 50 from the workpiece against the effect of the springs 35. When the support table assembly 18, workpieces 17, rods 34 and the frame 51 down to the active position and sawing begins, the frame 51 rests on the washers 47 provided on the rods 34 and thus remains in a fixed position relative to the workpiece 17 to cooperate with the lower portion 26 pieces to be sawed. The son 50 may also be replaced by blades, ribbons, strips, walls of a suitable thickness to be introduced into the sawing gaps 24 slices which are thus held in position without touching each other.

The variant illustrated in Figure 7 is a combination of the holding devices 22 according to the first and third embodiment. This variant comprises as holding members 25 on the one hand, two longitudinal bars 30 with elastomeric coatings 31 solicited against the parts to be sawed 17 thanks to the springs 35, and secondly, a frame 51 with son 50 which are arranged inside the sawing gaps 24. The frame 51 is fixed by means of intermediate pieces 52 on the sleepers 33 which cooperate with the springs 35 and the stationary stops 40. This variant is particularly effective since it ensures a double maintenance of sawn slices by external support and son intercalation.

The other components of this sawing device and its operation remain similar to the first embodiment.

The fourth embodiment illustrated in FIGS. 8 and 9 comprises a holding device 22 comprising a frame 60 in the shape of a U. The longitudinal branches 61 of this frame are intended to be applied laterally against the sawed slices 23 of the workpiece. sawing 17 by means of elastic pieces 62. The application and holding force can be obtained by means of a pneumatic device 63 comprising an inlet duct 64 and internal ducts 65 make it possible to inflate the elastic pieces 62. The force application can also be obtained by other means, such as mechanical clamping of the longitudinal legs 61 towards each other by means of a mechanical, pneumatic or hydraulic.

During a break in the wire, the frame 60 can be easily implemented by the handle 66 and then blocked by applying the clamping.

After repair of the wire, the latter can be disposed in the sawing gaps 24, since the width of the latter has remained constant. After removal of the frames 60, the sawing can be continued. Without the holding device 22, it would be impossible to re-thread the wire into the sawing gaps and the workpiece should be discarded.

A fifth embodiment is illustrated in Figures 10 to 13. In this embodiment the holding device 22 is mounted on the frame 10 of the sawing device and comprises a tray 70 whose bottom and / or walls can be perforated or provided with a flow so that the sawing liquid and the abrasive can be evacuated from the ferry. This tray is maintained by means of fasteners 71 on the frame 10 and provided with separating elements 72 intended to be introduced into the sawing gaps 24 between the sawed slices 23 to maintain exactly the gap between them.

In this embodiment, the separation elements 72 consist of a series of wires 73 stretched over a frame 74. The embodiment shown has two superposed frames 74, but any other number of frames 1 to 5 can be mounted in the bin 70.

Thus, the sawing can be carried out up to the temporary support 19 (FIG. 13), whereas the sawn slices 23 are maintained with a regular spacing, which ensures a high quality of the product without undulations, striations and irregularities. In addition the sawn slices are already separated from each other, which allows further processing and further conditioning.

These slices may, for example, be removed from the sawing device directly in the tray 70.

According to a favorable variant illustrated in FIG. 14, two drawers 81, 82 may be slidably housed in a tray 80 fixed to the frame 10.

Each of the drawers contains a holding device 22 for the slices of one or the other of the sawed ingots 17.

The bottom and the side walls of these drawers 81, 82 may be perforated for the flow of the sawing liquid. The latter may be retained in the tank 80 and discharged by a flow 84 with a valve 85.

The holding device 22 also comprises separating elements 72 intended to be introduced into the sawing gaps. These separating elements may consist of horizontal, oblique and / or diagonal son stretched on one, two or more frames 86. The son can thus constitute two crossed son plies.

The separating elements may also be constituted by vertical walls attached to the side walls of the drawers. After sawing, the drawers 81, 82 with sawn slices of each ingot may be removed from the sawing device.

It is understood that the embodiments described above are not limiting in nature and that they can receive any desirable modifications within the frame as defined by claim 1, in particular, one, two or more tables. support 18 may support one or more pieces to be sawed 17.

The relative movement between the support table or tables 18 and the sheet of son 15 may also be achieved by moving the sheet of son and any suitable mechanical, pneumatic, hydraulic means. The sawing movement can also be achieved in any other spatial direction than the vertical.

The first embodiment of Figures 1 to 3 may also include lateral clamping means instead of the vertical means.

The holding device 22 may be adapted to the shape of the workpiece. In the case of a circular section of this part, the maintenance can be obtained by a bar 30 fitting to the cylindrical surface.

The control of the application force can be achieved by any mechanical, pneumatic and hydraulic means with or without stationary stops.

The frame 51 of Figure 6 with its son or bands may also be mounted above Figure 4 of the tray 46, combining the second and third embodiments.

Several holding members 25, such as frames 51 or 60 may be superimposed to ensure a perfect fit under very difficult sawing conditions.

The separating elements 72 provided in the tray 70 or in the drawers 80 may be of any type horizontal son, oblique, diagonal, complete or partial walls, transverse bands, etc.

Claims (9)

1. Wire sawing device comprising at least one layer (15) of wires stretched out between at least two wire guide cylinders (11, 12) and held in position by grooves provided on the surface of said wire guide cylinders (11, 12) and defining the interval between the wires of said layer of wires, and hence the thickness of the sawed slices (23) being separated from each other by sawing gaps (24), the wires being adapted to move with alternating or continuous movement while bearing against at least one piece (17) to be sawed and held fixed on a support table (18), means (20, 21) being provided to accomplish a forward movement of the piece (17) to be sawed relative to the layer (15) of wires, the sawing device comprising a holding device (22) with holding members (25) adapted to coact with at least a portion of the slices being sawed, in order to maintain the partially or completely sawed slices (23) parallel to each other during the sawing, guide elements (34) being arranged on the support table (18) and the holding members (25) being mounted movably on these guide elements (34) so as to be moved from an inactive position toward an active position in which they coact with the slices (23) in the course of sawing, and vice versa, the holding members (25) being urged by resilient elements (35) in the direction of stationary abutments (40), characterised by the fact that the holding members (25) on the one hand are bearing against the stationary abutments (40) when in the inactive position, and on the other hand are spaced away from the stationary abutments (40) when in the active position, to coact with the piece or pieces (17) to be sawed, by the fact that the holding members (25) comprise at least one bar (30) extending along the piece (17) to be sawed, in a direction substantially parallel to the wire guide cylinders (11, 12), this bar (30) being provided with at least one coating (31) of elastomer intended to be applied against the slices (23) of the piece to be sawed, and by the fact that said bar (30) is mounted so as to swivel about a swivel axis (32) parallel to the wire guide cylinders (11, 12), onto crosspieces (33) mounted slidingly onto the guide elements (34).
2. Sawing device according to claim 1, characterised by the fact that the holding members (25) comprise a thick liquid or a gel (45) of a higher density than the machining liquid used, the thick liquid or gel (45) being contained in a vat (46) that in the active position is held so that said portion (26) of the slices is at least partially immersed into the thick liquid or the gel (45) so that the slices (23) are immobilised.
3. Sawing device according to claim 1, characterised by the fact that the holding device (22) comprises, as the holding members (25), separation elements (50, 72) intended to be at least partially introduced into the sawing gaps (24) between the slices (23) in order to hold the latter, these separation elements being mounted onto at least one support (51, 74, 86), by the fact that the separation elements are constituted by wires (50, 73), strips, blades, or walls of a thickness suitable for them to be introduced into said sawing gaps (24), and by the fact that said at least one support (51) is mounted onto the support table (18) and can be moved from the inactive position toward the active position.
4. Sawing device according to claim 3, characterised by the fact that said at least one support (51) is mounted above said bar (30).
5. Sawing device according to claims 2 and 3, characterised by the fact that said at least one support (51) is mounted above said vat (46).
6. Sawing device according to claim 3, characterised by the fact that said at least one support (51, 74, 86) is arranged in at least one vat (70, 80) mounted onto said frame (10).
7. Sawing device according to claim 6, characterised by the fact that it comprises at least two supports (86) arranged in at least two drawers (81) mounted slidingly into the vat (80).
8. Device according to claim 3, characterised by the fact that the wires (50, 73) are stretched out over the support (74, 86) in horizontal and/or oblique directions to form crossed layers of wires.
9. Sawing device according to claim 1, characterised by the fact that the holding device (22) comprises a U-shaped frame (60) whose longitudinal branches (61) are intended to be applied through resilient elements (62), laterally against the sawed slices (23).

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