JPH08168950A - Method and device for adjusting abrasive grain - Google Patents

Abstract

PURPOSE: To secure cutting accuracy while performing cutting operations repeatedly by causing a centrifugal force to act on a machining fluid for the separation of unground abrasive grains from chips of a workpiece to be cut and from ground abrasive grains, and reusing the unground abrasive grains separated. CONSTITUTION: A lid-equipped cylindrical container 13 is rotated at high speed so that an abrasive fluid is continuously fed from a tank 16 to a center portion through a feeder pipe 14 by a certain amount of flow by use of a pump 17. Since fine grains cause a centrifugal force that is smaller than their surface force, they overflow from the top of the container 13, are discharged into an overflow collecting container 15, and returned into the tank 16 through an abrasive-fluid return opening 18. As a result, a machining-fluid circulation system is formed, and only abrasive grains with large diameters are accumulated on the side face of the container 13, while chips and ground abrasive grains are accumulated in the machining fluid in the circulation system. The abrasive grains on the side face of the rotating container 13 are remixed with support oil and used for re-cutting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasive grain used for a multi-wire saw (hereinafter abbreviated as "wire saw") for cutting a material such as a semiconductor material or a ceramics into a large number of thin plate wafers with a wire and abrasive grains. The present invention relates to an adjusting method and device.

[0002]

2. Description of the Related Art A wire saw presses an object to be cut (hereinafter referred to as "workpiece") against a wire row having a predetermined pitch,
This is an apparatus for cutting a large number of wafers by a grinding action by pouring a working liquid containing abrasive grains (hereinafter referred to as “abrasive liquid”) and causing a wire and a work piece to move relative to each other.

FIG. 1 shows a perspective view of a cutting portion of a general wire saw, which is engraved at a predetermined pitch on the outer peripheral surfaces of three rotatably held groove rollers 1, 2, 3. One wire 4 is sequentially wound around the formed numerous groove grooves to form a wire row 5 having a predetermined pitch, and the wire row 5 is made to reciprocate or travel in one direction, and the work 6 or the wire row 5 is subjected to an abrasive liquid. While the polishing liquid 7 from the supply nozzle 12 is being applied, the work push-up base 10 is gradually raised and cut. In addition,
The work 6 is attached to a base 10 via a dummy plate 8 and fixed by a base fixing bolt 11.

The abrasive liquid 7 is a mixture of abrasive grains such as SiC and a supporting oil such as lapping oil. A dispersant and a thickener are appropriately added to prevent agglomeration while stirring in a tank (not shown). It is stored. The polishing liquid 7 is circulated and used, for example, after being supplied from the tank to the processing chamber provided with the wire saw by a pump, returned to the tank, and then supplied to the processing chamber again.

The grinding liquid scrapes the work little by little while being crushed between the traveling wire and the work. That is, in the course of continuous cutting, fine powder of abrasive grains of several microns to millimicrons or less or grinding fine powder of the work is generated, and these also circulate between the tank and the processing chamber. However, the fine abrasive powder and the work grinding powder do not contribute to cutting, and if they increase, they adhere to the abrasive and hinder the cutting action, which not only deteriorates the grinding efficiency but also makes it impossible for the wire. As a result of the force acting, the cutting accuracy represented by the warp deteriorates. Measures such as increasing the amount of the abrasive liquid in the tank are taken in order to mitigate the influence of these fine particles, but the same problem still occurs as the number of cuttings increases.

The conventional method has dealt with this problem by a method such as exchanging the abrasive liquid or adding new abrasive grains every predetermined number of times of cutting, but it is not economically preferable. Tokufair 4
There is also a method of removing a large amount of suspended fine particles from the polishing liquid returned from the processing chamber during cutting using a large amount of water as a medium liquid as in Japanese Patent Publication No. 16309, but it is not possible to remove submicron ultrafine particles. However, it is difficult to remove fine particles of several microns. In addition, the water-based abrasive liquid has a problem in that the cutting efficiency and the cutting accuracy are limited and the apparatus becomes large.

[0007]

A semiconductor material typified by silicon tends to be increased in size, and the amount of fine particles mixed in the abrasive liquid increases with one cutting, while the cutting accuracy is improved. It will be more and more severe. In addition, continuous cutting operation is required to increase productivity. It is an object of the present invention to develop a technique capable of removing fine particles from a used polishing liquid and ensuring cutting accuracy while repeatedly cutting.

[0008]

SUMMARY OF THE INVENTION Here, the gist of the present invention is to provide a plurality of incisions by pressing a wire row running while supplying a working fluid containing abrasive grains against an object to be cut, In the abrasive adjusting method of the working fluid of the wire saw for cutting into sliced pieces, centrifugal force is applied to the working fluid to separate the uncrushed abrasive from the chips of the material to be cut and the crushed abrasive, This is a method for adjusting the abrasive grains of a wire saw, characterized in that the separated uncrushed abrasive grains are reused.

From another aspect, the present invention provides a vertical annular centrifuge drum, a supply pipe for supplying a working fluid to the inside of the drum, and a working fluid overflowing from the upper side of the drum to the drum again. Comprising a machining fluid circulation system to deposit uncrushed abrasive grains on the inner surface of the drum, cutting chips of the workpiece and crushed abrasive grains to the supply pipe, the drum and the machining fluid circulation system. It is an abrasive grain adjusting device for a wire saw, characterized in that it is concentrated in a circulating working liquid or discharged together with the working liquid to the outside of the system.

[0010]

Next, the operation of the present invention will be described with reference to the accompanying drawings. Figure 2 shows the new Green Carborundum SiC # 60
0 An example of particle size distribution of abrasive grains is shown, and the average abrasive grain size is 25 μm.
Before and after, the distribution range is 10-60 μm.

FIG. 3 shows an example of the result of measuring the particle size distribution of the particles contained in the polishing liquid after the silicon having a diameter of 200 × 200 mm was cut once by a wire saw, and having a peak at 5 μm of 1 to 10 μm. The number of particles having a distribution in the range and sub-micron and milli-micron particles below that are increasing. These fine particles of 10 μm or less are fine abrasive powder or work grinding powder.

FIG. 4 shows the relationship between the number of times of cutting the same silicon and the amount of fine particles of 10 μm or less, and it can be seen that the fine particles accumulate as the number of times of cutting increases. FIG. 5 shows an example of the relationship between the number of cuts and the warp when a tank having a capacity of 100 liters is used. It can be seen that the warp sharply deteriorates when the number of cuts exceeds 5. For example, if an attempt is made to cut with a warp of 20 μm or less, the number of cuts will be 5 times. At this time
The ratio of fine particles of 10 μm or less is about 5 vol% from FIG.

Therefore, if the fine particles of 10 μm or less are removed by some method until the amount of fine particles reaches 5%, the polishing liquid can be used repeatedly. here,
The reason for removing fine particles of 10 μm or less is that the minimum grain size of the new abrasive grains shown in FIG. 2 is 10 μm. If this is 20 μm, remove fine particles of 20 μm or less from the used polishing liquid. Good. The smaller the abrasive grain size, the lower the grinding efficiency of the abrasive grains, but if fine grains of 10 μm to 20 μm are allowed, fine grains of 10 μm or less may be removed. Note that the work grinding powder is generally 5 μm or less, so if the main purpose is to remove it, 5 μm
Fine particles of m or less may be removed. A centrifugal separation method is used as a method for removing such fine particles.

FIG. 6 shows an example of a centrifuge. In the figure,
A cylindrical container 13 having a donut-shaped lid (hereinafter, referred to as a rotary container) that constitutes a vertical annular centrifuge drum is rotated at high speed, and a tank 16 is used to pump a pump 17 to a central portion of a supply pipe 14 to be ground. Liquid is continuously supplied at a certain flow rate. The polishing liquid is subjected to the action of centrifugal force when flowing upward in the cylindrical container 13. The specific shape of the rotator container 13 is not limited to a particular one as long as the centrifugal action is exerted.

Since the fine particles have a centrifugal force smaller than the surface force, they are not trapped on the side surface of the rotating body container 13 and are not caught.
It is discharged from the upper part of 13 as an overflow flow into the overflow recovery container 15 and returns to the tank 16 via the polishing liquid return port 18. As a result, the working fluid circulation system is formed, and the rotating container
On the side surface of 13, only the abrasive grains having a large grain size are accumulated, while the cutting fluid and the crushed abrasive grains are accumulated in the working fluid in the circulation system.
The abrasive grains on the side surface of the rotary container 13 are mixed again with the supporting oil and used for re-cutting.

Classification point of the centrifuge (boundary particle diameter between particles captured on the side surface of the rotary container 13 and particles flowing out)
May be set according to the angular velocity of the rotating body container 13 and the supply flow rate of the polishing liquid. Thereby, the abrasive grains can be divided into any size.

If the supporting fluid is added to the polishing liquid to dilute it before centrifuging, the abrasive grains and fine grains are easily dispersed, so that the centrifugal separation effect is enhanced. If the classification is incomplete even after the centrifugation is performed once, it is sufficient to add the supporting oil to the recovered abrasive grains to dilute them, and then re-execute the centrifugal separator. Of course, this may be repeated. It goes without saying that the above method can also be applied when adjusting the particle size distribution of new abrasive grains to a desired one.

For example, cutting processing and centrifugation can be performed by using a grinding chamber and a polishing liquid supply system for the centrifuge as shown in FIG. At the time of cutting, the valve 22-a is opened and the valve 22-b is closed, and the pump 21 is used to supply the abrasive liquid to the processing chamber. To centrifuge, first the valve 22-a is closed and the valve 22-b is opened, and the polishing liquid is stored in the centrifugal separation tank 16. Next, with the valve 20-a open and the valve 20-b closed, the rotary container 13 is rotated while circulating the polishing liquid using the centrifugal pump 17 to perform centrifugal separation. When the rotary container 13 is filled with the abrasive grains, the rotary container 13 is stopped and the abrasive grains are taken out. The process is repeated until the abrasive grains are not accumulated in the rotating body container 13. Then the valve
20-a is closed and valve 20-b is opened to discharge the working fluid containing chips and crushed abrasive grains. The steps from to are repeated until the polishing liquid in the polishing liquid tank 23 is exhausted. In addition, reference numerals 19 and 24 denote agitators, and the same reference numerals as those in FIG. 6 denote the same members.

FIG. 12 shows an example of an operation of taking out the abrasive grains from the rotary body container 13. As shown in FIG. 12 (a), there is a method in which the cloth bag 26 is mounted inside the rotary body container 13, is centrifuged, and after the rotary body container is stopped, the abrasive grains are taken out together with the cloth bag 26. Also, FIG.
Overflow collection container with a hole in the bottom as shown in (b)
If 15 and the rotator container 13 are used, the abrasive particles can be scraped downward by the scraping device 27 after the centrifugal separation while rotating the rotator container at a low speed. Next, the function and effect of the present invention will be described in more detail with reference to Examples.

[0020]

【Example】

(Example 1) As shown in FIG. 4, the abrasive liquid used for cutting 10 times in succession contained about 13 wt% of abrasive grains of 10 μm or less.
After the specific gravity was adjusted to 1.30 by diluting this polishing liquid, the rotor cylinder 13 shown in FIG. 6 which is a centrifugal separation drum with an inner diameter a = 150 mm.
10 of the abrasive grains deposited inside the drum after centrifugation using a
Table 1 shows the results of examining the proportion of abrasive grains having a size of μm or less. Centrifuge rotary drum dimensions: a = 150, b = 200, h = 15
0 (mm) Upper: content of abrasive grains of 10 μm or less (%) Lower: recovery of abrasive grains (%)

[0021]

[Table 1]

When the rotation speed of the drum is as high as 800 rpm, centrifugal force is increased, and thus abrasive grains of 10 μm or less are deposited inside the drum. Further, when the rotation speed of the drum is as low as 600 rpm, the recovery rate of the abrasive grains becomes poor as the flow rate increases.

After the abrasive liquid used for cutting was continuously diluted 10 times to adjust the specific gravity to 1.30, it was centrifuged using a centrifuge drum having an inner diameter a = 400 mm to remove the abrasive grains in the inside of the drum. Table 2 shows the results of examining the ratio of abrasive grains having a size of 10 μm or less. Centrifuge rotary drum dimensions: a = 400, b = 530, h = 20
0 (mm) Upper: content of abrasive grains of 10 μm or less (%) Lower: recovery of abrasive grains (%)

[0024]

[Table 2]

Table 3 shows the ratio of the abrasive grains of 10 μm or less in the abrasive grains deposited on the inner side of the drums at various drum sizes.

[0026]

[Table 3]

As the size of the drum increases, the agitation state of the abrasive liquid improves, so that the content of abrasive grains of 10 μm or less decreases. However, if the drum size increases too much, the amount of the circulating abrasive liquid increases too much, which makes stable circulation difficult, and conversely reduces the separation ability. Therefore, the drum dimension a is 150-40
0 mm is suitable.

(Embodiment 2) Sectional diameter 200 mm, length 180 mm
Silicon ingot of green carborundum SiC
# 600 Abrasive 100 consisting of 130 kg of abrasive grains and lapping oil
Using liter, wire diameter 0.18mm, wire pitch 1.15
mm, the number of wire rows is 150, after cutting 4 times continuously,
After centrifugation (with a classification point of 10 μm), the recovered abrasive grains were mixed with lapping oil to make a polishing liquid, and the cutting was performed thereafter. At this time, the size of the centrifuge drum, a = 400
, B = 500, h = 200, rotation speed 600 rpm, flow rate 50 liters /
Minutes

FIG. 7 shows the result of measuring the ratio of fine particles of 10 μm or less in the polishing liquid for each cutting number, which is 5v until the 7th cutting.
It was possible to control below ol%. In order to carry out the eighth cutting, it is necessary to remove fine particles of 10 μm or less by centrifugation again. FIG. 8 shows the average value of the warpage for each number of cuts. As can be seen from this, in this example, 17 μ
We were able to continue cutting with a warp of m or less.

On the other hand, in the conventional method, a total of 260 kg of abrasive grains was required to replace the abrasive liquid after the fourth cutting and perform the cutting seven times. That is, by using the method of the present invention, the amount of abrasive grains used could be reduced by half.

Example 3 Cross-sectional diameter 170 mm, length 300 mm
Of quartz ingot of green carborundum SiC # 60
0 Using 100 liter of abrasive liquid consisting of 130 kg of abrasive grains and lapping oil, wire diameter 0.20 mm, wire pitch 1.6 mm,
It cut | disconnecting 4 times continuously on condition of the wire row number 150. Then, 100 liters of lapping oil was added to the polishing liquid to dilute it and then centrifuged. The centrifuge drum size, rotation speed, and flow rate were the same as in Example 1. The recovered abrasive grains and lapping oil were mixed to prepare a polishing liquid, and the cutting was subsequently performed.

FIG. 9 shows the results of measuring the proportion of fine particles of 10 μm or less in the polishing liquid for each number of cuts. Compared with Example 1, the proportion of fine particles of 10 μm or less in the polishing liquid used for the fifth time was measured. Is 1v
Although it is as small as ol%, this is the effect of diluting the polishing liquid before centrifugation. For this reason, the proportion of fine particles of 10 μm or less in the polishing liquid could be suppressed to 5 vol% or less until the eighth cutting, which is one more than in Example 1. Figure 10 shows the average value of the warpage for each number of cuts.
We were able to continue cutting with a warp of m or less.

[0033]

According to the conventional method, in order to maintain high cutting accuracy and to continue the cutting, it is necessary to replace the abrasive liquid every several cuttings, and the running cost for the abrasive grains is large. According to the present invention, stable high-speed continuous cutting can be performed at low cost even for large diameter cutting of φ200 or more.

[Brief description of drawings]

FIG. 1 is a front perspective view illustrating a cutting state of a work having a circular cross section.

FIG. 2 is a particle size distribution graph showing an example of the particle size distribution of new green carborundum SiC # 600 abrasive grains.

FIG. 3 is a particle size distribution graph showing an example of the result of measuring the particle size distribution in the polishing liquid after cutting once.

FIG. 4 is a graph showing changes in the proportion of fine particles of 10 μm or less in continuous cutting by a conventional method.

FIG. 5 is a graph showing changes in warpage during continuous cutting according to a conventional method.

FIG. 6 is a schematic explanatory view of a centrifuge used in the present invention.

FIG. 7: 10μ in continuous cutting of silicon by the method of the present invention
6 is a graph showing an example of changes in the proportion of fine particles of m or less.

FIG. 8 is a graph showing an example of changes in warpage during continuous silicon cutting according to the method of the present invention.

FIG. 9 is a graph showing an example of changes in the proportion of fine particles of 10 μm or less in continuous quartz cutting according to the method of the present invention.

FIG. 10 is a graph showing an example of changes in warpage during continuous quartz cutting according to the method of the present invention.

FIG. 11 is an explanatory diagram showing an example of a polishing liquid supply system to a processing chamber and a centrifuge.

FIG. 12 is an explanatory diagram showing an example of an operation of taking out abrasive grains from the centrifugal separator.

[Explanation of symbols]

 1, 2, 3: Groove roller 16: Centrifuge tank 4: Wire 17: Centrifuge pump 5: Wire row 18: Abrasive fluid return port 6: Workpiece 19: Stirrer 7: Abrasive fluid 20: Valve 8: Dummy plate 21: Pump 9: Base 22: Valve 10: Push-up base 23: Abrasive fluid tank 11: Base fixing bolt 24: Stirrer 12: Abrasive fluid supply nozzle 25: Abrasive fluid return port 13: Rotating body container 26: Cloth bag 14: Abrasive fluid Supply pipe 27: Abrasive scraping device 15: Overflow collection container

Claims (2)

[Claims] 1. A method for adjusting an abrasive grain of a working fluid of a wire saw, in which a wire row running while supplying a working fluid containing abrasive grains is pressed against an object to be cut to provide a plurality of cuts or a plurality of sliced pieces are cut. In, the centrifugal force is applied to the working liquid to separate the uncrushed abrasive grains from the chips of the object to be cut and the crushed abrasive grains, and the separated uncrushed abrasive grains are reused. How to adjust the abrasive grain of the wire saw. 2. A vertical annular centrifuge drum, a supply pipe for supplying the working liquid to the inside of the drum, and a working liquid circulation system for supplying the working liquid overflowing from the upper side of the drum to the drum again. The uncrushed abrasive grains are deposited on the inner surface of the drum, and the chips of the object to be cut and the crushed abrasive grains are concentrated into a working fluid that circulates through the supply pipe, the drum, and the working fluid circulation system. Alternatively, an abrasive grain adjusting device for a wire saw, which is discharged out of the system together with the working liquid.