JP2010029998A - Method and device for treating coolant used for fixed abrasive grain wire saw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of treating a coolant used for a fixed abrasive grain wire saw and a treatment device for the coolant capable of collecting chips of an object to be cut from the coolant after use highly efficiently, extending the lifetime of a fixed abrasive grain wire, and improving the cut face accuracy. <P>SOLUTION: The coolant used in cutting a work to be cut by the fixed abrasive grain wire saw 21 is introduced to a centrifugal separator 25 is separated into foreign materials mainly having coarse chips and chip-contained liquid containing fine chips, the foreign materials mainly having the coarse chips are discharged from a port at one end in the longitudinal direction of the centrifugal separator and collected in a chip collection tank 23, and a chip-contained liquid is discharged from an overflow port at the other end in the longitudinal direction of the centrifugal separator 25 and reused as the coolant. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method and apparatus for treating a coolant used in a fixed abrasive wire saw, and in particular, an abrasive used for cutting, slicing, internal polishing, dicing, and ingot cutting of hard materials such as silicon, quartz, and ceramic. The present invention relates to a coolant processing method and a processing apparatus used for cutting in a wire saw using a fixed abrasive wire in which grains are fixed to a wire.

  Conventionally, a wire saw has been used as means for cutting a workpiece to be cut into slices. With this wire saw, a thin wire row to which tension is applied is run, and an object to be cut (for example, a silicon ingot) is pressed against the wire row while spraying a slurry-like abrasive containing abrasive grains on the wire row, It is an apparatus that cuts an object to be cut into wafers by the polishing action of loose abrasive grains, and since it is possible to obtain a plurality of wafers at the same time, it is also called a multi-cutting method. FIG. 7 shows a schematic configuration of a multi-wire saw used for processing single crystal silicon as an example.

  Referring briefly to FIG. 7, the wire 42 supplied from the feeding bobbin 41 passes through a plurality of guide rollers 43 for guiding the wire, and a plurality of grooved rollers 44 having a plurality of grooves form a wire array having a predetermined pitch. The object to be cut 46 is cut into a wafer by spraying slurry containing loose abrasive grains from the nozzle 47 toward the wire row while pressing the object to be cut 46 by the feed unit 45 against the wire row. Thereafter, the wire row is wound around a winding bobbin 49 through a number of guide rollers 48. The wire 42 travels by the driving force of the driving motor 50 attached to the grooved roller 44. At this time, the movement information of the dancer rollers 51 and 52 is fed back to the rotation of the feeding bobbin 41 and the take-up bobbin 49, and is constant. The tension is maintained. Usually, the wire 42 moves forward while performing a certain bidirectional traveling or one-way traveling according to a request from the viewpoint of quality such as effective use as a material and improvement in cut surface roughness, and is finally wound around the winding bobbin 49. .

  In the case of cutting using loose abrasive grains as described above, the free abrasive grain-containing slurry is expected to cool the abrasive grains whose temperature is increased by the cutting operation. This is because if the temperature of the abrasive grains rises above a certain level, the abrasive grains are accelerated and the sharpness deteriorates, so the abrasive grains must be cooled to an appropriate temperature. However, the slurry containing loose abrasive grains accumulates various substances such as chips from the workpiece, crushed abrasive grains, and iron from the worn wire. Decreases and the sharpness of the abrasive grains is lowered without suppressing the temperature rise of the abrasive grains.

  Furthermore, the largest market where wire saw cutting technology is applied is in the field of cutting silicon ingots for semiconductors and solar cells, and in recent years there has been a shortage of polysilicon as the material to be cut. An important theme is how to efficiently recover silicon powder, which is a cutting powder.

  Therefore, in the case of cutting using free abrasive grains, Patent Document 1 discloses in advance removal of water-soluble coolant from a used slurry in a silicon wafer manufacturing process, which contains at least water-soluble coolant, abrasive grains, and silicon grains. To obtain a water-soluble coolant remaining in the solid using a low-boiling organic solvent having a compatibility with the water-soluble coolant and having a boiling point lower than that of the water-soluble coolant. The proposal of extracting, removing the low boiling-point organic solvent used for extraction by centrifugation, and collect | recovering solid content obtained by centrifugation is disclosed.

In addition, as a method of cutting using free abrasive grains, Patent Document 2 discloses a coarse mixed liquid containing recovered abrasive grains by guiding the used abrasive slurry used in a wire saw to a first centrifuge. Are separated into a fine mixed liquid containing fine cutting scraps and crushed abrasive grains, the coarse mixed liquid is guided to a second centrifuge, and further the cutting scraps and crushed abrasive grains adhering to the surface of the recovered abrasive grains Is separated from the recovered abrasive grains, the recovered abrasive mixed liquid and the fine mixed liquid are separated, and the fine mixed liquid taken out from the first centrifuge and the fine mixed liquid taken out from the second centrifuge Are separated through a high-density electric field to separate the fine solid and the recovered cutting liquid, and the recovered abrasive mixed liquid separated by the second centrifuge and the recovered cutting liquid separated by the high-density electric field; And reuse as abrasive slurry There is disclosed a proposal.
JP 2007-246367 A JP-A-11-172237

  In the first place, as shown in FIG. 7, the method of cutting using slurry-like free abrasive grains has the disadvantage that the abrasive grains are scattered on the workbench and dried to contaminate the work environment, and waste liquid treatment and Extra processing such as the need to clean the cut wafer is necessary. In addition, the slurry containing free abrasive grains contains various kinds of substances such as abrasive grains (generally SiC abrasive grains are often used), crushed abrasive grains, and iron of worn wires. It is not easy to recover silicon powder, which is the cut powder of the workpiece, from the inside. Moreover, since the slurry containing free abrasive grains has a high viscosity, a special solvent is used as described in Patent Document 1, or two centrifuges are used as described in Patent Document 2. However, it is difficult to efficiently recover the silicon powder.

  On the other hand, multi-wire saws using fixed abrasive wires with abrasive grains fixed to the wire are technologies that are expected to be used in the slicing market such as silicon ingots and sapphire ingots as an alternative to conventional slicing methods using loose abrasive grains. It is. In general, diamond that is the hardest among minerals is used as abrasive grains for actual cutting operation in a fixed abrasive wire. However, no matter how hard the diamond is, it is inevitable that it will wear due to repeated cutting operations. The cause of wear of diamond abrasive grains is the heat generated during slicing. How to supply sufficient coolant to the fixed abrasive wire and effectively absorb the heat generated in the diamond abrasive grains during cutting. The point is whether it can be done. However, by circulating the coolant, foreign matter such as chips from the object to be cut, crushed abrasive grains, and worn-out metal parts accumulate in the coolant. As a result, the wear of the diamond abrasive grains is promoted without suppressing the temperature rise of the diamond abrasive grains, and the life of the fixed abrasive wire is reduced. In addition, accumulation of foreign matter such as cutting waste in the coolant loses the performance of the coolant and lowers the slicing accuracy.

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is to collect chips from a coolant in a multi-wire saw using a fixed abrasive wire with high efficiency. Another object of the present invention is to provide a coolant processing method and a processing apparatus for a fixed abrasive wire saw that can extend the life of a fixed abrasive wire and realize high-precision slicing.

  In order to achieve the above object, the coolant processing method used in the fixed abrasive wire saw according to the present invention introduces the coolant used when cutting the workpiece to be cut in the fixed abrasive wire saw to the centrifuge, and is coarse. Foreign matter mainly consisting of cutting waste and liquid containing cutting waste containing fine cutting waste are separated, and foreign matter mainly consisting of coarse cutting waste is discharged from the opening at one end in the longitudinal direction of the centrifuge. Then, it is collected in a cutting waste collecting tank, and the cutting waste containing liquid is discharged from the overflow opening at the other end in the longitudinal direction of the centrifugal separator and reused as a coolant.

  Further, the coolant processing apparatus used in the fixed abrasive wire saw of the present invention is mainly composed of a fixed abrasive wire saw, a coolant tank, a cutting waste recovery tank, a separation liquid tank, and a cutting waste containing coolant. A centrifuge that separates the foreign material into a cutting waste-containing liquid containing fine cutting waste, a replenishing coolant tank, a first pipe that guides the coolant used in the fixed abrasive wire saw to the coolant tank, and the coolant tank A second pipe for leading the cutting waste-containing coolant to the centrifuge, a third pipe for guiding foreign matter mainly consisting of coarse cutting waste discharged from the centrifuge to the cutting waste recovery tank, and a second discharge pipe from the centrifuge A fourth pipe for leading the cutting waste-containing liquid containing fine cutting waste to the separation liquid tank, and a fifth pipe for guiding the separation liquid in the separation liquid tank to the coolant tank And a sixth pipe that guides the coolant in the replenishing coolant tank to the coolant tank, and a seventh pipe that guides the coolant in the coolant tank to the coolant supply means of the fixed abrasive wire saw. One end of the centrifuge has an opening for discharging foreign matters mainly coarse cutting waste after centrifugation, and the other end in the longitudinal direction of the centrifuge contains fine cutting waste after centrifugation. It is characterized by having an overflow opening for discharging the contained cutting waste-containing liquid.

  Since the processing method and the processing apparatus of the coolant used for the fixed abrasive wire saw of the present invention are configured as described above, the coolant is supplied to the traveling fixed abrasive wire and the fixed abrasive wire is to be cut. Fixed abrasive wire saw that presses a workpiece and cuts the workpiece. Used coolant containing coarse and fine cutting waste, foreign material mainly containing coarse cutting waste, and fine cutting waste. In the coolant, the foreign matter mainly consisting of coarse cutting waste is recovered in the cutting waste recovery tank, and the cutting waste containing liquid containing fine cutting waste is reused as coolant. Foreign matter accumulates on the surface and the concentration of foreign matter in the coolant does not increase. It is possible to realize a chair.

  The wire used for the fixed abrasive wire is not particularly limited as long as it can be electroplated and its strength and elastic modulus can withstand the tension between the guide roller and the grooved roller. Examples thereof include a steel wire such as a piano wire of a scale, and a metal wire such as a tungsten wire and a molybdenum wire.

  The diameter of the wire used in the present invention can be appropriately selected depending on the shape and characteristics of the object to be cut, and usually about 0.05 to 0.5 mm is often adopted, but a fine wire of 0.05 mm or less Even if it is a thick line exceeding 0.05 mm, the effect of the present invention is the same.

Examples of the present invention will be described below. However, the present invention is not limited to the following examples, and can be appropriately changed and modified without departing from the technical scope of the present invention.
(1) Production of Fixed Abrasive Wire by Electroplating A fixed abrasive wire was produced by a plating apparatus having a schematic configuration as shown in FIG. That is, a steel wire 2 having a diameter of 160 μm is fed from the feeder 1, and the steel wire 2 is alkali-degritted with an alkali degreasing tank (an alkaline degreasing agent having a pH of 11) and pickled (sulfuric acid having a pH of 1). 4. Wash with water in water washing tank 5, pre-treat with water in pre-treatment tank (bath composition of nickel sulfamate tetrahydrate 600 g / liter, pH 4.2) 6, The surface was plated with 7 μm thick nickel in the plating tank 7. The composition of the plating bath in the plating tank 7 is 600 g / liter of nickel sulfamate tetrahydrate, 55 g / liter of nickel chloride hexahydrate, 30 g / liter of boric acid as a pH buffering agent, type 1 gloss Abrasive agent (saccharin) 15 ml / liter, Type 2 brightener (2-butyne-1,4 diol) 50 ml / liter, and nickel abrasive grains (coated nickel) with a particle size of 15-25 μm pre-coated with nickel The plating conditions were such that the pH was 3.0, the temperature was 55 ° C., and the current density was 45 A / dm ² . The current efficiency at this time was 90%.

Thereafter, the steel wire 2 on which the nickel plating film was formed was washed with a water rinsing tank 8, and then the steel wire 2 with diamond abrasive grains fixed in the nickel plating film was wound around a winder 9.
(2) Fixed Abrasive Wire Saw FIG. 2 is a schematic configuration diagram showing an example of a wire saw using the fixed abrasive wire obtained as described above. This wire saw has a wire feeding bobbin 11a, a number of guide rollers 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j, 12k, grooved rollers 13, 14, coolant supply means 15 and wire take-up A bobbin 11b is provided. 16 is a workpiece to be cut (for example, a semiconductor ingot), 17 is a workpiece holding means, 18 is a workpiece feed motor, and 19 is a wire. The workpiece feed motor 18 can freely lift and lower the workpiece holding means 17 holding the workpiece 16 to be cut.
(3) Coolant Processing Device Used for Fixed Abrasive Wire Saw FIG. 3 is a schematic configuration diagram showing an example of a coolant processing device used for the fixed abrasive wire saw. In FIG. 3, 21 is a fixed abrasive wire saw, 22 is a coolant tank, 23 is a cutting waste recovery tank, 24 is a separation liquid tank, 25 is a centrifuge (see FIG. 4 for a schematic configuration), 26 is a supply coolant tank, 27a Is a first pipe that guides the coolant used in the fixed abrasive wire saw 21 to the coolant tank 22, 27 b is a second pipe that guides the coolant containing the cutting waste in the coolant tank 22 to the centrifuge 25, and 27 c is discharged from the centrifuge 25. A third pipe 27d for guiding foreign matter mainly made of the coarse cutting waste 28a (for example, silicon powder) to the cutting waste collection tank 23, 27d contains cutting waste containing fine cutting waste discharged from the centrifuge 25 A fourth pipe 27e for guiding the liquid to the separation liquid tank 24, and a fifth pipe 27e for guiding the separation liquid in the separation liquid tank 24 to the coolant tank 22. , 27f is a sixth pipe for guiding the new coolant in the replenishing coolant tank 26 to the coolant tank 22, and 27g is for guiding the coolant in the coolant tank 22 to the coolant supply means (reference numeral 15 in FIG. 2) of the fixed abrasive wire saw 21. The seventh pipe 27h is an eighth pipe that guides the new coolant to the supply coolant tank 26, and 27i is a ninth pipe that guides pure water to the supply coolant tank 26. P represents a pump.
(4) Centrifuge FIG. 4 is a diagram showing a schematic configuration of the centrifuge 25 (see FIG. 3). In FIG. 4, reference numeral 29 denotes an outer shell, and one end portion in the longitudinal direction of the outer shell 29 has an opening 30 for discharging foreign matters mainly composed of coarse cutting waste 28 a after centrifugation. The other end in the longitudinal direction has an overflow opening 31 for discharging cutting waste containing liquid containing fine cutting waste after centrifugation. A shaft 29a extends from the other end of the outer shell 29, and the shaft 29a can be rotated in the direction of the arrow by a motor (not shown).

  A coolant receiving pipe 32 is inserted into the outer shell 29 by cutting out one end of the outer shell 29. The coolant receiving pipe 32 can be rotated integrally with the outer shell 29 at the same rotational speed in the same direction by a motor (not shown).

  A second pipe 27 b for introducing the coolant in the coolant tank 22 is inserted into the coolant receiving pipe 32, and a ring-shaped packing 33 is interposed in the gap between the second pipe 27 b and the coolant receiving pipe 32 to seal it. Is secured. The coolant receiving pipe 32 is provided with an opening 32 a for discharging coolant containing cutting waste toward the inner wall of the outer shell 29.

A plurality of ring-shaped partition walls 34 a and 34 b are installed between the coolant receiving pipe 32 and the outer shell 29. A ring-shaped baffle plate 35 that is slightly inclined to the right is attached to the ring-shaped partition walls 34a and 34b. As shown in FIGS. 5A and 5B, a plurality of openings 36 are provided in the ring-shaped partition walls 34 a and 34 b on the inner side from the place where the ring-shaped baffle plate 35 is attached.
(5) Treatment method of coolant used in fixed abrasive wire saw According to the fixed abrasive wire saw configured as described above, in FIG. 2, the wire 19 fed out from the wire feed bobbin 11a is guided by the guide rollers 12a and 12b. , 12c, 12d, 12e, 12f and the grooved roller 13 to reach the coolant supply means 15. The coolant supplied to the wire 19 from the coolant supply means 15 absorbs heat generated by the cutting of the diamond abrasive grains fixed to the wire 19 to the coolant, thereby suppressing the temperature rise of the diamond abrasive grains and suppressing wear. The life of the fixed abrasive wire can be extended.

  The wire 19 is wound around the outer peripheral surfaces of the grooved rollers 13 and 14 in a spiral manner, and then wound around the wire winding bobbin 11b through the guide rollers 12g, 12h, 12i, 12j, and 12k. In addition, the groove | channel for winding a wire spirally is formed in the outer peripheral surface of the rollers 13 and 14 with a groove | channel. A coolant (in the present embodiment, containing mineral oil, an anionic surfactant and water) is supplied to the wire row between the grooved rollers 13 and 14 from the coolant supply means 15. The wire row between the grooved rollers 13 and 14 is cut into a large number of wafers by the workpiece feed motor 18 coming into contact with the workpiece holding means 17 and the workpiece 16 to be cut that descends at an appropriate speed. The temperature rise of the diamond abrasive grains fixed to the wire 19 in the cutting process is effectively suppressed by the action of the coolant described above.

  In the above description, the case where the wire 19 travels in one direction from the feeding bobbin 11a to the winding bobbin 11b has been described. However, the wire 19 travels from the feeding bobbin 11a to the winding bobbin 11b and from the winding bobbin 11b to the feeding bobbin. It is also possible to perform bi-directional travel that alternately repeats the case of heading to 11a and finally wind it around the winding bobbin 11b. In the case of this bidirectional traveling, it is preferable to provide a coolant supply means between the workpiece 16 to be cut and the grooved roller 14.

  The coolant used for the fixed abrasive wire saw is processed as described below.

  As shown in FIG. 3, the coolant supplied to the wire (reference number 19 in FIG. 2) from the coolant supply means (reference number 15 in FIG. 2) of the fixed abrasive wire saw 21 is collected in the collecting pipe, and then the first It is guided to the coolant tank 22 through the pipe 27a. The cutting waste-containing coolant in the coolant tank 22 is guided to the centrifuge 25 through the second pipe 27b, and after being subjected to a centrifugal separation process as will be described later, the foreign matter mainly composed of coarse cutting waste 28a is third. The cutting waste containing liquid containing fine cutting waste is guided to the separation liquid tank 24 via the fourth pipe 27d through the pipe 27c. The separation liquid in the separation liquid tank 24 is guided to the coolant tank 22 through the fifth pipe 27e. In order to adjust the concentration and amount of the coolant as required, the replenishing coolant tank 26 is appropriately replenished with a new liquid coolant via the eighth pipe 27h and is appropriately reinforced with pure water via the ninth pipe 27i. . The new liquid coolant in the replenishing coolant tank 26 is guided to the coolant tank 22 through the sixth pipe 27f. The coolant in the coolant tank 22 is guided to the coolant supply means (reference number 15 in FIG. 2) of the fixed abrasive wire saw 21 through the seventh pipe 27g.

  The coolant guided to the centrifuge 25 through the second pipe 27b is processed as follows.

  In FIG. 4, the coolant 37 containing the cutting waste in the second pipe 27 b is discharged into the coolant receiving pipe 32. Since the coolant receiving pipe 32 is integrated with the outer shell 29 and is rotated in the same direction at the same rotational speed, the coolant 37 discharged into the coolant receiving pipe 32 is constant from the opening 32 a provided in the coolant receiving pipe 32. It is discharged toward the outer shell 29 at the timing. In the flow of the coolant 37 containing the cutting waste discharged into the outer shell 29 as described above, the flow reaching the overflow opening 31 on the right side in FIG. 4 will be described first.

  As shown in FIG. 5 (a), the ring-shaped partition wall 34a is provided with a plurality of openings 36 on the inner side from the place where the ring-shaped baffle plate 35 is attached. The cutting waste and coolant of a size that can pass through the partition wall 34a can enter the right partition surrounded by the partition wall 34a and the partition wall 34a. However, since the baffle plate 35 is attached to the partition wall 34 a, the cutting waste and coolant that has passed over the baffle plate 35 stays in contact with the inner surface of the outer shell 29. Thereafter, similarly, cutting scraps and coolant of a size that can pass through the opening 36 provided in the ring-shaped partition wall 34a pass through the partition wall 34a and are surrounded by the partition wall 34a and the partition wall 34a. You can enter the further right section. However, since the baffle plate 35 is attached to the partition wall 34 a, the cutting waste and coolant that has passed over the baffle plate 35 stays in contact with the inner surface of the outer shell 29. In this way, when the liquid level of the coolant 37 staying in contact with the inner side surface of the outer shell 29 is high enough to overcome the lower end surface 31 a of the overflow opening 31, a coolant (separating liquid) containing fine cutting scraps. Is discharged from the overflow opening 31 toward the fourth pipe 27d. As a result of selecting cutting scraps of a size that can be passed by the opening 36 provided in the partition wall 34a and the baffle plate 35, a section close to the overflow opening 31 among the sections surrounded by the partition wall 34a and the partition wall 34a. In the coolant, there are relatively small foreign matters such as crushed abrasive grains and worn wire metal, mainly fine cutting waste 28b, and coarse cutting waste is present in the coolant far from the overflow opening 31. 28a exists.

  Next, the flow reaching the opening 30 on the left side in FIG. 4 in the flow of the coolant 37 containing the cutting waste discharged into the outer shell 29 will be described.

When coolant containing cutting waste is discharged into the outer shell 29 from the opening 32a at a constant timing, the outer shell 29 rotates together with the coolant receiving pipe 32, so that the cutting waste is contained in the outer shell 29 by centrifugal force. When pressed against the wall surface, the small cuttings clump together and try to form a large lump. However, since the baffle plate 35 is attached to the partition wall 34a, the cutting waste having a size that can pass through the opening 36 provided in the partition wall 34a among the cutting waste that has passed over the baffle plate 35 and Coolant enters the left compartment. Of the cutting waste that has entered the left compartment, the cutting waste of a size that can pass over the baffle plate 35 attached to the ring-shaped partition wall 34b and pass through the opening 36 provided in the partition wall 34b is the partition wall. After passing through 34b, the vehicle enters the left compartment surrounded by the partition wall 34b and the partition wall 34b. However, since such an opening does not exist in the baffle plate 35, the baffle plate 35 passes over the baffle plate 35 and passes through the opening 36 provided in the ring-shaped partition wall 34b in the cutting waste that is aggregated into a large lump. The cutting waste having a size that can be passed through the partition wall 34b and can enter a further left section surrounded by the partition wall 34b and the partition wall 34b. Further, as shown in FIG. 4, the outer shell 29 has an outer diameter that decreases in a tapered manner toward the opening 30, and the opening 30 is at a high position when viewed in the vertical direction with respect to the overflow opening 31. In the section surrounded by the partition wall 34b and the partition wall 34b, there is almost no coolant in the section close to the opening 30, and most of the foreign matter is mainly coarse cutting waste 28a. In this way, the foreign matter mainly consisting of coarse cutting waste 28a reaching the opening 30 is discharged toward the third pipe 27c.
(6) Confirmation of cutting scrap recovery effect a. Target Liquid As an example of the present invention, using the centrifuge shown in FIG. 4, a coolant comprising the above composition (containing mineral oil, an anionic surfactant and water) used for cutting a fixed abrasive wire saw. As a comparative example, the weight (kg / liter) of the coolant per unit volume was investigated when the coolant was not centrifuged.
b. Cutting target and cutting time The process of cutting a wafer having a square cross section (having a height of 156 mm and a width of 156 mm) and a rectangular silicon ingot having a length of 200 mm and a thickness of 0.2 mm was repeated. . Note that one silicon wafer was cut out continuously for 3 hours.
c. Wire saw and coolant processing apparatus An apparatus having the structure shown in FIG. 3 was used. In this cutting operation, in both the embodiment and the comparative example, pure water is not replenished from the ninth pipe 27i to the replenishing coolant tank 26, and new coolant is appropriately replenished from the eighth pipe 27h to the replenishing coolant tank 26. The fresh liquid coolant in the replenishing coolant tank 26 was guided to the coolant tank 22 through the sixth pipe 27f.

In the comparative example, since the centrifugal separation was not performed, the coolant used for cutting the fixed abrasive wire saw was supplied to the coolant tank 22 through the first pipe 27a, and the coolant in the coolant tank 22 was the seventh pipe 27g. And then returned to the coolant supply means of the fixed abrasive wire saw 21. Therefore, in the comparative example, the coolant in the coolant tank 22 is not guided to the centrifuge 25 through the second pipe 27b, and the separated liquid in the separated liquid tank 24 is transferred to the coolant tank 22 through the fifth pipe 27e. There was no guidance.
d. Centrifugation conditions The centrifugal force is 2000 G, and the amount of coolant supplied to the centrifuge is 197 liters / hour.
e. Centrifugation results As described above, the weight per unit volume of the coolant (kg) when the coolant used for cutting the silicon ingot with the fixed abrasive wire saw is centrifuged and when the coolant is not centrifuged. / Liter) is shown in FIG. 6, the vertical axis indicates the weight per unit volume of the coolant in the coolant tank 22 (kg / liter) in the apparatus of FIG. 3, and the horizontal axis indicates 0 when the cutting operation starts, 1, 2, 3, 4, 5, and 6 indicate the end of the 3-hour continuous cutting operation of the first, second, third, fourth, fifth, and sixth silicon wafers, respectively. At the start of the cutting operation, the coolant is in the state of a new liquid and does not contain foreign matter, but the cutting operation takes longer time, and the coolant contains chips from the object to be cut, crushed abrasive grains, and iron from the worn wire. As a result of accumulation of foreign matter such as the coolant, the cooling action of the coolant is reduced, the temperature rise of the diamond abrasive grains cannot be suppressed, the wear of the diamond abrasive grains is promoted, and the life of the fixed abrasive wire is reduced. As the amount of foreign matter such as chips of the workpiece contained in the coolant increases, the weight (kg / liter) per unit volume of the coolant increases. Therefore, the change in the properties of the coolant can be known by looking at the change in the weight per unit volume (kg / liter) of the coolant.

  In FIG. 6, the symbol “◯” indicates the case where the centrifugation is performed (Example), and the symbol “●” indicates the case where the centrifugation is not performed (Comparative Example). By performing centrifugation according to the method of the present invention, as shown in FIG. 6, the weight per unit volume of the coolant (kg / liter) hardly changes, and it is used for a long time for cutting a silicon ingot in a fixed abrasive wire saw. Even so, it can be seen that the properties of the coolant do not change.

  However, when the coolant used for cutting the silicon ingot in the fixed abrasive wire saw is not centrifuged according to the method of the present invention, the numerical value of the weight per unit volume of the coolant (kg / liter) is as shown in FIG. As the cutting operation time becomes longer, it surely increases, and it can be seen that foreign matter such as chips of the object to be cut accumulates in the coolant without centrifugation.

  Table 1 below shows the results of fluorescent X-ray quantitative analysis of the components (% by weight) of the cutting waste in the cutting waste collection tank 23 at the end of the third silicon wafer continuous cutting operation for 3 hours.

表１に明らかなように、切削屑中の大部分はＳｉであり、切削屑からシリコン粉を高効率で回収することが可能である。なお、表１において、Ｃａ、ＰおよびＡｌはクーラントの成分である。

As is apparent from Table 1, most of the cutting waste is Si, and silicon powder can be recovered from the cutting waste with high efficiency. In Table 1, Ca, P and Al are coolant components.

  As is apparent from the detailed description above, according to the method and apparatus of the present invention, it is understood that the properties of the coolant do not change even when the fixed abrasive wire saw is cut for a long time. It is also possible to recover silicon powder from cutting waste separated by centrifugation with high efficiency.

  The method and apparatus of the present invention can be used for the treatment of coolant used in fixed abrasive wire saws used for cutting, slicing, internal polishing, dicing, and ingot cutting of hard materials such as silicon, quartz, and ceramics.

FIG. 1 is a schematic configuration diagram of a plating apparatus suitable for manufacturing a fixed abrasive wire. FIG. 2 is a schematic diagram showing an example of a fixed abrasive wire saw. FIG. 3 is a schematic configuration diagram showing an example of a coolant processing apparatus used in the fixed abrasive wire saw. FIG. 4 is a diagram showing a schematic configuration of the centrifuge. FIGS. 5A and 5B are views showing openings provided in a ring-shaped partition wall. FIG. 6 is a diagram showing the relationship between the cutting operation time and the weight (kg / liter) per unit volume of the coolant in the fixed abrasive wire saw. FIG. 7 is a schematic configuration diagram of a general multi-wire saw.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Feeder 2 Steel wire 3 Alkali degreasing tank 4 Pickling tank 5 Washing tank 6 Pretreatment tank 7 Plating tank 8 Washing tank 9 Winding machine 11a Wire feeding bobbin 11b Wire winding bobbin 12a, 12b, 12c, 12d, 12e 12f, 12g, 12h, 12i, 12j, 12k Guide roller 13, 14 Grooved roller 15 Coolant supply means 16 Work to be cut 17 Work holding means 18 Work feed motor 19 Wire 21 Fixed abrasive wire saw 22 Coolant tank 23 Cutting waste collection Tank 24 Separating liquid tank 25 Centrifuge 26 Supply coolant tank 27a 1st pipe 27b 2nd pipe 27c 3rd pipe 27d 4th pipe 27e 5th pipe 27f 6th pipe 27g 7th pipe 27h 8th pipe 27i 9th pipe P Pump 8a Coarse cutting waste 28b Fine cutting waste 29 Outer shell 29a Shaft 30 Opening 31 Overflow opening 32 Coolant receiving pipe 33 Packing 34a, 34b Partition wall 35 Baffle plate 36 Opening 37 Coolant 41 Feeding bobbin 42 Wire 43 Guide roller 44 Groove roller 45 Feed unit 46 Workpiece 47 Nozzle 48 Guide roller 49 Winding bobbin 50 Drive motor 51 Dancer roller 52 Dancer roller

Claims (2)

  In the fixed abrasive wire saw, the coolant used when cutting the workpiece to be cut is guided to a centrifuge, and separated into foreign matter mainly composed of coarse cutting waste and liquid containing cutting waste containing fine cutting waste. The foreign matter mainly consisting of coarse cutting waste is discharged from the opening at one end in the longitudinal direction of the centrifuge and collected in the cutting waste recovery tank, and the cutting waste-containing liquid is collected in the other longitudinal direction of the centrifuge. A method for treating a coolant used in a fixed abrasive wire saw, wherein the coolant is discharged from an overflow opening at an end and reused as a coolant.   Separating fixed abrasive wire saw, coolant tank, cutting waste collection tank, separation liquid tank, cutting waste containing coolant into foreign matter mainly consisting of coarse cutting waste and cutting waste containing liquid containing fine cutting waste Centrifuge, replenishment coolant tank, first pipe that guides coolant used in the fixed abrasive wire saw to the coolant tank, second pipe that guides coolant containing cutting waste in the coolant tank to the centrifuge, and centrifugal separation A third pipe for guiding foreign matter mainly composed of coarse cutting waste discharged from the machine to the cutting waste collection tank, and a cutting waste-containing liquid containing fine cutting waste discharged from the centrifugal separator to the separation liquid tank The fourth pipe, the fifth pipe for guiding the separated liquid in the separated liquid tank to the coolant tank, and the new liquid coolant in the replenishing coolant tank for the coolant tank A sixth pipe for guiding, and a seventh pipe for guiding the coolant in the coolant tank to the coolant supply means of the fixed abrasive wire saw, and at one end in the longitudinal direction of the centrifuge, coarse cutting waste after centrifugation The other end of the centrifuge in the longitudinal direction has an overflow opening for discharging cutting waste-containing liquid containing fine cutting waste after centrifugation. Coolant processing equipment used for the fixed abrasive wire saw.

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