EP1437209A1 - 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 comprising at least one ply of wires stretched between at least two wire guide cylinders and held in position by grooves provided on the surface of said cylinders thread guides which define the interval between the threads of said ply of threads, therefore the thickness of the sawn slices separated from each other by interstices sawing, the wires being able to move in an alternating movement or continuous pressing against at least one workpiece to be sawn fixed on a support table.

Wire sawing devices of the aforementioned type with displacement of the wires of the ply of wire or of the workpiece are already known, especially in the electronic components industry of ferrites, quartz and silicas, for obtaining thin slices of materials such as poly- or monocrystalline 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 others techniques such as diamond disc sawing.

In known devices, the sawing zone consists of an assembly at least two cylinders placed in parallel. These cylinders, called wire guides, are engraved with grooves defining the interval between the wires of the tablecloth, that is the thickness of the slices. The workpiece is fixed on a support table which moves perpendicular to the wire layer. Travel speed defines cutting speed. The renewal of the thread, as well as the control of its tension is done in a part called wire management zone located outside the zone sawing proper. The agent which will govern the cutting is either an abrasive fixed on the wire, a free abrasive brought in the form of slip. The wire only acts as carrier. When cutting the workpiece into thin slices, the tensioned wire is both guided and pulled by the thread guide cylinders.

For many applications, sawn wafers are very thin compared to the diameter of the workpiece. The slices sawn so have significant flexibility and can bend and bend to come into contact with neighboring slices. These deflections are harmful for the precision and flatness of the cut and can induce undulations, unwanted streaks and irregularities on the surface of sawn edges. These irregularities, even a few micrometers are enough to make the wafers for certain applications, such as silicon for the solar industry and semiconductors. The deformations of the edges can even induce micro-cracks 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 lumber gaps, which in turn leads to variations in slice thickness, sawing speed and wire wear, therefore an additional increase in surface irregularities 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 which touch or whose the sawing gap has become very small. It is then necessary to throw the coin to be sawed in the event of wire breakage and to restart sawing with a new one piece, which results in a considerable loss of materials, often very expensive and sawing time.

The object of the present invention is to remedy these major drawbacks and the invention is characterized for this purpose by the fact that the sawing device comprises a holding device arranged so as to maintain, during the sawing, the partially or entirely sawn slices substantially parallel between them and so that the width of the sawing gaps is preserved substantially constant during sawing of the slices.

Thanks to these characteristics, it is possible to obtain slices of a great flatness, without undesirable undulations, streaks and irregularities. The micro-cracks and breaks are completely avoided.

Because the sawing gaps are kept at a constant width, obtains a supply and distribution of regular free abrasive, therefore sawing regular without ripples and at constant speed from a sawing slot to the next.

The wire is also worn regularly, so it is less subject to disruptions. In the event that a break should appear, the device according to the invention can also help with easy wire repair and wire replacement in the sawing gaps, therefore to avoid rejection of the workpiece following a wire break.

Advantageously, the holding device comprises organs of holding likely to cooperate with at least a portion of the slices in sawing track.

This effectively secures the slices during sawing.

According to a favorable embodiment, the holding device comprises guide elements arranged on the support table, the holding members being movably mounted on the guide members to be moved from an inactive position to an active position, in which they cooperate with the slices being sawed, and vice versa.

These characteristics allow a reliable and precise construction.

Advantageously, the holding members are stressed by elastic elements in the direction of stationary stops.

These characteristics allow automatic operation of the holding device with a reduced number of components.

Favorably, the holding organs are on the one hand in the position inactive, pressing against the stationary stops and, on the other hand, in the position active, away from stationary stops to cooperate with the part or parts to cut.

According to a favorable embodiment, the holding members include at least one bar extending along the workpiece in a direction substantially parallel to the wire guide cylinders, this bar being provided at least one elastomer coating intended to be applied against slices of the workpiece.

Advantageously, said bar is pivotally mounted along an axis of pivoting parallel to the wire guide cylinders on cross members mounted so sliding on the guide elements.

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

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

These characteristics of the holding device make it possible to obtain a original and inexpensive solution to remedy the drawbacks of undulations and the aforementioned surface irregularities.

Alternatively, the holding device may also include as that members for holding the separation elements intended to be introduced into the less partially in the sawing gaps between the slices for maintain the latter, these separating elements being mounted on at least a support.

Thanks to these characteristics, the gap between the slices can be maintained constant very precisely, even in the case of external forces acting on the slices in process of sawing.

Favorably, the separating elements consist of wires, strips, strips or walls of adequate thickness to be able to be introduced into said sawing gaps.

Maintaining and separating the sawn edges is thus achieved by simple and efficient way.

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

These characteristics allow easier integration of the sections sawn in a production line.

Another embodiment is characterized in that the device for support is constituted by a U-shaped frame whose branches longitudinal are intended to be applied laterally against sawn edges by means of elastic parts.

Such a frame can be mounted and removed by lateral displacement during sawing of the room; this mode of execution is therefore particularly useful in the event of a break saw wire. During the repair, the gaps between the sections can be kept constant thanks to this device and the wire can be easily replaced and reintroduced between sections after repair. In addition, the frame can also be used for transporting the workpiece after sawing it before and during heel cutout by which the slices are held on a support temporary cutting. The slices, separated from each other by a gap regular, do not adhere to neighboring slices and can be cleaned and detached very easily.

Other advantages emerge from the characteristics expressed in the dependent claims and the following description of the invention further in detail using drawings which represent schematically and as example several embodiments and variants.

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

Figure 2 is an enlarged partial front view of this first mode execution.

FIG. 3 is a side view of the holding device in FIG. 2. Figure 4 is a partial front view of a second embodiment.

Figures 5 and 6 show a third embodiment for partial face and partial perspective.

FIG. 7 is a partial front view of a variant combining the first and third embodiments.

Figures 8 and 9 illustrate a fourth perspective embodiment and in partial front view.

Figures 10 to 13 show a fifth embodiment in perspective, side view, front view at the start and end of sawing.

Figure 14 shows a variant of the previous embodiment.

Referring to Figures 1 to 3, the sawing device according to the first mode of execution includes a frame 10 and wire guide cylinders 11, 12, here in number two, mounted on this frame with their axes arranged in parallel, being well understood that the device could have more than two wire guide cylinders.

The wire 14 is unwound from a supply reel, not shown, and then wound around the wire guide cylinders in any possible winding mode to form at least one ply of parallel wires 15 in a sawing zone. The wire is then recovered in a suitable device not illustrated, such as a coil receptor or a drip tray.

One, two or more pieces to be sawed 17, such as ingots in one hard material, are mounted on a support table 18 by means of a temporary support 19.

This support table 18 can be moved vertically in the direction Z thanks to a column 21 and a motor 20 to support the pieces to be sawed 17 against the ply of wires 15.

The periphery of the wire guide cylinders 11, 12 is engraved with grooves which define the interval between the neighboring wires of the wire layer 15, therefore the thickness sawn slices. These are separated from each other by sawing slots or gaps.

The wire 14 is tensioned and both guided and pulled by the wire guide cylinders to move in an alternating back and forth or continuous movement. This thread is favorably made of spring steel with a diameter between 0.1 and 0.2 mm in order to saw blocks of hard materials or more composition particular, such as silicon, ceramic, composed of elements of groups III-V and II-VI, GGG (Gadolinium-Gallium Garnet), sapphire, etc., in 0.1 increments about 5 mm thick. The abrasive agent is a commercial product and can be diamond, silicon carbide, alumina, etc., in a form attached to the wire or in free form suspended in a liquid which serves as a transporter for abrasive particles.

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

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

These holding members 25 include in the embodiment of the Figures 1 to 3 a longitudinal bar 30 per workpiece extending along the latter in a direction substantially perpendicular to the wires of the ply of wires 15. The bars 30 are provided with coatings 31 of elastomer intended to be applied against the edges of the pieces to be sawed.

Each bar 30 is pivotally mounted along a pivot axis 32 parallel to the wire guide cylinders 11, 12 on crosspieces 33. Thus, the coverings 31 can optimally adapt to the workpiece 17. The sleepers 33 slide on rods 34 serving as integral guide elements of the support table 18. Elastic means in the form of coil springs 35 urge the crosspieces 33 and the longitudinal bars 30 towards one hand sawing parts 17 and secondly stationary stops 40 integral with the frame 10.

When the workpieces are in a high position away from the ply of wires 15, the crosspieces 33 are supported on the stationary stops 40, and the holding members 25 are in this inactive position away from the parts to saw 17.

These sawing parts 17 are lowered for sawing into contact with the ply of threads 15. After sawing a minimum distance of one centimeter for example, the elastomeric coatings 31 come into contact with the parts to saw and keep the sawn slices firmly in this active position 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 stops stationary 40 allow to determine exactly the position in which, the holding members 25 come into action.

Sawing can then continue to the opposite end of the workpiece, while the sawed edges 23 are held in position, to avoid ripples, streaks and other irregularities due to transverse movements of the sections. Saw slots or gaps 24 have a constant width allowing a regular supply of abrasive particles and a constant sawing speed.

The embodiment illustrated in FIG. 4 is similar to that of FIGS. 1 to 3, except that the holding device 22 is of a different type. Indeed, the retaining members 25 in this case comprise a thick liquid or a gel 45 higher density than the machining fluid used. This thick liquid or gel is contained in a tray 46 which is fixed on the cross members 33 mounted sliding on the rods 34. It is possible, for example, to use silicones with a viscosity adequate.

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

A third embodiment illustrated in Figures 5 and 6 includes as that retaining member 25 of the separation elements 54 intended to be introduced at least partially in the interstices 24 between the sections 23 to maintain these last. In the illustrated mode, a series of wires 50 is stretched over a frame 51 and arranged parallel to the wires of the wire web 15. In the active position, these wires 50 are introduced into the sawing gaps 24 between the edges 23 to maintain exactly the gap between them. 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, sawing parts 17, rods 34 and the frame 51 descends to the active position and the sawing begins, the frame 51 rests on the lock washers 47 provided on the rods 34 and thus remains in a fixed position relative to the parts to be sawed 17 so as to cooperate with the lower portion 26 of the parts to be sawed. The sons 50 could also be replaced by blades, ribbons, strips, walls of a adequate thickness to be inserted into the sawing gaps 24 slices which are thus held in position without touching each other.

The variant illustrated in FIG. 7 is a combination of the holding 22 according to the first and third embodiment. This variant comprises as holding members 25 on the one hand, two bars longitudinal 30 with elastomeric coatings 31 biased against pieces to be sawed 17 thanks to the springs 35, and on the other hand, a frame 51 with wires 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 double support of the slices sawn by external support and by intercalation of wires.

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

The fourth embodiment illustrated in Figures 8 and 9 includes a holding device 22 comprising a U-shaped frame 60. The branches longitudinal 61 of this frame are intended to be applied laterally against sawn edges 23 of the workpiece 17 by means of elastic parts 62. The force of application and maintenance can be obtained by means of a device pneumatic 63 comprising an inlet duct 64 and internal ducts 65 allow the elastic parts 62 to be inflated. The application force may also be obtained by other means, such as mechanical tightening of longitudinal branches 61 towards each other by means of a control mechanical, pneumatic or hydraulic.

When the wire breaks, the frame 60 can be put in place easily thanks to the handle 66 and then blocked by application of the tightening.

After repairing the wire, it can be placed in the interstices of sawing 24, since the width of the latter has remained constant. After removal of the frames 60, sawing can be continued. Without the device holding 22, it would be impossible to thread the thread again in the interstices of sawing and the workpiece should therefore be thrown away.

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 device saw 10 and comprises a bin 70 whose bottom and / or walls can be perforated or provided with a flow so that the sawing liquid and the abrasive can be removed from the bin. This bin is maintained thanks to elements of fixing 71 on the frame 10 and provided with separation elements 72 intended to be introduced into the sawing gaps 24 between the sawed edges 23 for maintain exactly the gap between them.

The separation elements 72 are in this embodiment constituted by a series of wires 73 stretched over a frame 74. The embodiment shown has two superimposed frames 74, but any other number of frames from 1 to 5 can be mounted in tray 70.

Thus, sawing can be carried out up to the temporary support 19 (FIG. 13), while the sawn slices 23 are maintained with a regular spacing, this which ensures high product quality without ripples, streaks and irregularities. In addition, the sawn slices are already separated from each other, which allows easier treatment and subsequent conditioning.

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

According to a favorable variant illustrated in FIG. 14, two drawers 81, 82 can 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 can be perforated for the flow of sawing liquid. The latter can be retained in the bin 80 and evacuated by a flow 84 with a valve 85.

The holding device 22 also comprises elements of separation 72 intended to be introduced into the sawing gaps. These separating elements may consist of horizontal, oblique wires and / or diagonals stretched over one, two or more frames 86. The wires can thus constitute two layers of crossed threads.

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

It is understood that the embodiments described above do not have no limiting nature and that they can receive any modifications desirable within the framework as defined by claim 1, In particular, one, two or more support tables 18 can support one or more than two workpieces 17.

The relative movement between the support table or tables 18 and the ply of wires 15 could also be achieved by moving the ply of wires and by any adequate mechanical, pneumatic, hydraulic means. The movement of sawing can also be carried out in any other spatial direction than the vertical.

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

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

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

The frame 51 of FIG. 6 with its wires or bands can also be mounted above figure 4 of the tank 46, combining the second and the third modes of execution.

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

The separating elements 72 provided in the tank 70 or in the drawers 80 may be of any kind horizontal, oblique, diagonal, wall wires complete or partial, transverse bands, etc.

Claims (17)

Wire sawing device comprising at least one ply of wires (15) stretched 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) which define the interval between the threads of said ply of threads, therefore the thickness of the sawed edges (23) separated from each other by sawing interstices (24), the threads being capable of moving in an alternating movement or continuous in abutment against at least one workpiece (17) fixed on a support table (18), means (20, 21) being provided to effect a relative advance movement between the workpiece (17) and the ply of wires (15), characterized in that the sawing device comprises a holding device (22) arranged so as to maintain, during sawing, the sections (23) partially or entirely sawn substantially parallel to one another and so that the width of the interstices s sawing (24) is kept substantially constant during sawing of the slices. Sawing device according to claim 1, characterized in that the holding device (22) comprises holding members (25) capable of cooperating with at least a portion of the slices in the process of sawing. Sawing device according to claim 2, characterized in that the holding device (22) comprises guide elements (34) arranged on the support table (18), the holding members (25) being movably mounted on the guide elements (34) to be moved from an inactive position to an active position, in which they cooperate with the edges (23) during sawing, and vice versa. Sawing device according to claim 3, characterized in that the holding members (25) are urged by elastic elements (35) in the direction of stationary stops (40). Sawing device according to claim 4, characterized in that the holding members (25) are, on the one hand in the inactive position, in abutment against the stationary stops (40) and, on the other hand in the active position , separated from the stationary stops (40) to cooperate with the part or parts to be sawed (17). Sawing device according to claim 5, characterized in that the holding members (25) comprise at least one bar (30) extending along the workpiece (17) in a direction substantially parallel to the guide rollers son (11, 12), this bar (30) being provided with at least one coating (31) of elastomer intended to be applied against the edges (23) of the workpiece. Sawing device according to claim 6, characterized in that the said bar (30) is pivotally mounted along a pivot axis (32) parallel to the wire guide cylinders (11, 12) on crossmembers (33) slidably mounted on the guide elements (34). Sawing device according to claim 5, characterized in that the holding members (25) comprise a thick liquid or gel (45) of a higher density than the machining liquid used, the thick liquid or gel (45 ) being contained in a tank (46) maintained in the active position such that said portion (26) of the slices is at least partially immersed in the thick liquid or the gel (45) so that the slices (23) are immobilized. Sawing device according to claim 1 or 2, characterized in that the holding device (22) comprises, as the holding member (25), separating elements (54, 72) intended to be introduced at least partially into the sawing gaps (24) between the edges (23) to maintain the latter, these separating elements being mounted on at least one support (51, 74, 86). Sawing device according to claim 9, characterized in that the separating elements consist of wires (50, 73), strips, blades or walls of an adequate thickness to be able to be introduced into said sawing gaps (24). Sawing device according to claims 5 and 9, characterized in that said at least one support (51) is mounted on the support table (18) and can be moved from the inactive position to the active position. Sawing device according to claims 6 and 11, characterized in that said at least one support (51) is mounted above said bar (30). Sawing device according to claims 8 and 11, characterized in that said at least one support (51) is mounted above said bin (46). Sawing device according to claim 9, characterized in that said at least one support (74, 86) is arranged in at least one tray (70, 80) mounted on said frame (10). Sawing device according to claim 14, characterized in that it comprises at least two supports (86) arranged in at least two drawers (81) slidably mounted in the tray (80). Device according to claim 10, characterized in that the wires (50, 73) are stretched on the support (74, 86) in horizontal and / or oblique directions and / or to form plies of crossed wires. Sawing device according to claim 1, characterized in that the holding device is constituted by a U-shaped frame (60) whose longitudinal branches (61) are intended to be applied laterally against the sawn edges (23) by means of elastic parts (62).

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