JPH0929605A - Detection method and device for specific gravity of working fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To alleviate the burden of a worker and improve the reliability of measurement by enabling an automatic detection of the specific gravity of working liquid reserved in a container reserving a working liquid through a sensor detecting a load detector set under the container and the surface position of the liquid. SOLUTION: A wire saw is cut into a plurality of thin plate-shaped wafers by the lapping of slurry 54 stored in a tank 52 when a semiconductor ingot is pushed against wire trains running at high speed after a work feeding table is moved in a cut feed direction. A specific gravity detection device for the slurry 54 is composed of a ultrasonic sensor 64, stirring motor 66, stirring bane (impeller) 68, load cell (load detector) 70, computing unit 72, and a display. The unit 72 divides the slurry weight detected by the cell 70 by the slurry volume obtained from the data stored in the sensor 64 and a memory part to calculate the specific gravity of the slurry 54 and output the same to the display 74.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a working fluid specific gravity detecting method and apparatus, and more particularly to a working fluid specific gravity detecting method and apparatus for automatically detecting the specific gravity of a working fluid (slurry) containing abrasive grains used in a wire saw. Regarding

[0002]

2. Description of the Related Art A wire saw is one of the cutting devices for cutting a workpiece such as a semiconductor ingot or ceramic into a number of thin plates. As a working liquid (slurry) used for cutting in this wire saw, an oily slurry in which abrasive grains are mixed with oil, an aqueous slurry in which abrasive grains are mixed with a water-soluble liquid, and the like are known. Since the mixing ratio of these slurries has a great influence on the cutting property, it is necessary to accurately control the mixing ratio so that the mixing ratio is appropriate. Conventionally, the management of this slurry has been mainly performed based on the specific gravity of the liquid.

Generally, as a specific gravity meter for measuring the specific gravity of a liquid, a hollow glass body, a body portion, a spherical portion filled with spherical particles such as lead, and a scale paper with a specific gravity scale are sealed and fixed. A gravitational buoy consisting of the cervix is used. This hydrometer knows the specific gravity of the liquid by floating the liquid on the liquid and reading the volume of the liquid sinked on a scale attached to the neck.

Conventionally, after mixing the slurry, an operator puts the above-mentioned specific gravity meter into the slurry and reads the scale to detect the specific gravity.

[0005]

However, in the conventional detection method using the hydrometer, the operator has to open the upper lid of the tank in which the slurry is stored and insert the hydrometer each time, which is troublesome. In addition, there is a problem that the measurement results vary depending on how the hydrometer is dropped into the liquid. Further, since the slurry liquid adheres to the scale of the hydrometer and the scale is difficult to read, there is a problem in terms of measurement accuracy.

Furthermore, in the conventional method as described above,
There is a problem that it cannot be applied to the automation of wire saw cutting. The present invention has been made in view of such circumstances,
An object of the present invention is to provide a machining fluid specific gravity detection device capable of accurately and automatically detecting the specific gravity of a machining fluid containing abrasive grains used in a wire saw and adapting to automation of the wire saw.

[0007]

In order to achieve the above object, the present invention forms a wire row by winding a wire that reciprocates between a pair of wire reels around a plurality of grooved rollers, and forms the wire row. In a wire saw that cuts the workpiece into a large number of wafers by pressing the workpiece while supplying a machining fluid containing abrasive grains to the wafer, a load detector is provided in a container that stores the machining liquid, The weight of the working fluid stored in the container is detected by a detector, and the position of the liquid level of the working fluid stored in the container is also detected by a sensor. The correspondence with the volume of the stored machining fluid is stored in the computing device,
The weight detected by the load detector and the position detected by the sensor are input to the arithmetic device, and the arithmetic device stores the weight in the container from the position of the liquid level detected by the sensor and the correspondence. It is characterized in that the volume of the working fluid is obtained, and the specific gravity value of the working fluid is calculated based on the obtained volume and the weight detected by the load detector.

According to the present invention, the weight of the working fluid is detected by the load detector while the working fluid is contained in the container, and the position of the liquid level of the working fluid stored in the container (the liquid level (Equivalent to the height) is detected by the sensor and these results are notified to the arithmetic unit. Since the arithmetic device previously stores the correspondence between the position of the liquid surface and the volume of the machining liquid stored at that time in the form of table data, functions, etc., the sensor detects using this correspondence. The volume of the working liquid stored in the container can be determined from the position of the liquid level. Then, the specific gravity of the working fluid can be calculated by dividing the weight of the working fluid detected by the load detector by the obtained volume. The result can be output to a display or output to various control systems for use.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a method and apparatus for detecting a specific gravity of a working fluid according to the present invention will be described below in detail with reference to the accompanying drawings. First, a wire saw to which the working fluid specific gravity detection device according to the present invention is applied will be described. FIG. 1 is an overall configuration diagram of the wire saw 10. As shown in the figure, the wire 1 wound around the wire reel 12 on the left side of the figure.
4 is a traverse device 16 and a plurality of fixed guide rollers 1
, And the dancer roller 20, and are successively wound around the grooved rollers 22A, 22B, 22C.
Then, the wire row 24 is provided between the grooved rollers 22B and 22C.
After being formed, the wire 14 is wound around the other wire reel 26 through the plurality of fixed guide rollers 18, 18 ..., The dancer roller 20, and the traverse device 16 on the right side of the drawing.

The wire reels 12 and 26 are respectively connected to drive motors 28 and 30 which can rotate in the forward and reverse directions, and a drive motor 32 which can also rotate in the forward and reverse directions to the grooved roller 22A.
Are connected. Then, these drive motors 28, 3
By driving 0 and 32, the wire 14 is reciprocated between the one wire reel 12 and the other wire reel 26.

A weight 34 having a predetermined weight is hung on the dancer roller 20 to constantly apply a required tension to the traveling wire 14. A work feed table 36 is provided below the wire row 24, and the work feed table 36 can be moved in a cutting feed direction (Y-Y direction in the drawing) by a screw rod 40 rotated by a motor 38. And the wire row 2 of the work feed table 36
A semiconductor ingot 42, which is a workpiece, is supported on the fourth side via a work block 44 and a slice base 48.

Slurry supply nozzles 50, 50 are arranged at both ends of the wire row 24, and a slurry storage tank 52 is provided.
A machining liquid (slurry) 54 containing abrasive grains stored in the above is supplied to the wire row 24 from the slurry supply nozzles 50, 50 via a pump 56 and an appropriate piping system 58. still,
The abrasive grains used are, for example, those of GC # 600 to # 1000. The slurry 54 supplied to the wire row 24 is recovered by a recovery tray (not shown) installed below the wire row 24 and returned to the slurry storage tank 52 again. That is, the slurry 54 is circulated and supplied to the wire row 24.

Then, when the work feed table 36 is moved in the cutting feed direction (the wire row 24 side), the semiconductor ingot 42 is pressed against the wire row 24 running at high speed, and the semiconductor ingot 42 pressed against the wire row 24. Is cut into a large number of thin wafers by the lapping action of the slurry 54. Further, wire cleaning devices 60, 60 are provided in the middle of the wire traveling path, and the wire cleaning devices 60, 60 remove the slurry 54 adhering to the wire 14.

FIG. 2 is a schematic view of the essential parts of the specific gravity detecting device for the slurry 54 stored in the slurry storage tank 52. The specific gravity detection device shown in the figure mainly includes an ultrasonic sensor 64, a stirring motor 66, a stirring blade (impeller) 68,
The load cell (load detector) 70, a computing device 72, a display 74 and the like are included. The ultrasonic sensor 64 is
It is fixed to the upper lid 53 of the slurry storage tank 52 and detects the height of the liquid surface 55 of the slurry 54. Incidentally, the reading value of the ultrasonic sensor 64 is set with the liquid level position as a reference position zero when the slurry 54 has a predetermined capacity, and the actual liquid level height is detected from the reference position plus・ Detected as a negative relative amount. Then, the detection result is notified to the arithmetic unit 72.

The stirring motor 66 is provided on the upper lid 53 and is connected to an impeller 68 via a shaft 67. By driving the stirring motor 66, the impeller 68 is rotated about the shaft 67. The slurry 54 can be evenly stirred. The slurry storage tank 52
A load cell 70 is disposed in the lower part of the load cell 70 to detect the load applied to the bottom surface of the slurry storage tank 52, that is, the weight of the slurry 54 including the weight of the slurry storage tank 52. In addition, the load cell 70 is generally a prismatic shape or a quadrangular shape or the like, and a strain gauge is bonded to a strain generating body (processed so as to generate elastic deformation by receiving a force) to form a bridge circuit, thereby applying a load. It is converted into voltage and measured, and accuracy up to about 1/5000 can be obtained. The measurement range is determined by the size and shape of the strain generating element, and there are various forms such as a magnetostrictive type and a capacitance type in addition to the strain gauge. Further, the load cell 70 is connected to the arithmetic unit 72, and notifies the arithmetic unit 72 of the detected weight of the slurry.

The arithmetic unit 72 has a storage unit (not shown), can store the data detected by the load cell 70, and can store the slurry storage tank 5 therein.
2, the function V = f (B) indicating the relationship between the liquid level height (B) and the volume (V) of the machining liquid stored in the slurry storage tank 52 at that time is stored in advance. The relationship between the height of the liquid surface (B) and the volume of the working liquid (V) is
It may be preliminarily tested or grasped by calculating the volume from the internal shape of the slurry storage tank 52, and not only the function but also the table data may be stored. Thereby, the volume (V) of the working liquid can be obtained from the height (B) of the liquid surface.

Then, the arithmetic unit 72 divides the slurry weight detected by the load cell 70 by the slurry volume obtained from the data stored in the ultrasonic sensor 64 and the storage unit to obtain the slurry 54. The specific gravity is calculated and the result is output to the display device 74. In addition to displaying the specific gravity value of the slurry 54 as it is, the indicator 74 may determine whether the abrasive grains or oil (solution) is excessive or insufficient, and perform a display prompting adjustment of mixing.

Further, the slurry storage tank 52 can be easily moved to another place by the moving roller 77. Next, the operation of the machining fluid specific gravity detecting device configured as described above will be described. First, the weight (WC) of the slurry storage tank 52 without the slurry 54 (the slurry storage tank 52 is empty)
Is detected by the load cell 70 and stored in the storage unit of the arithmetic unit 72. Next, the slurry 54 is put into the slurry storage tank 52, the stirring motor 66 is driven, and the impeller 68 is rotated so that the abrasive grains are mixed uniformly, and the liquid is stirred. And
The total weight (WA) with the slurry 54 inserted is detected by the load cell 70. At this time, the total weight (WA)
It is possible to know the weight of only the slurry 54 by subtracting the weight (WC) of only the slurry storage tank 52 stored in the storage unit from.

Subsequently, the stirring motor 66 is stopped to stop the stirring by the impeller 68, and the slurry liquid level 55 is stabilized. After the liquid surface 55 has been shaken up and down, the ultrasonic sensor 64 measures the liquid level (B). The arithmetic unit 72 uses the data of the liquid level height (B) detected by the ultrasonic sensor 64 and the function V = f (B), and the weight (WC), (WA) detected by the load cell 70. Based on the following equation, the specific gravity value of the slurry 54 can be calculated by the following formula: Specific gravity value = (WA-WC) / f (B). Then, by displaying the calculated specific gravity value on the display 74, the operator can easily confirm the specific gravity value of the slurry 54.

Further, the specific gravity value of the slurry is not limited to simply being displayed on the display 74, and this value is fed back to the control device of the wire saw 10 to detect an abnormal specific gravity value when the specific gravity value of the slurry is not an appropriate value. It is conceivable to give an alarm to notify. Further, it may be configured such that the slurry having an appropriate specific gravity value is automatically blended by feeding back to the control system for adjusting and feeding the abrasive grains or the solution forming the slurry.

In the above-mentioned embodiment, in the detection of the height (B) of the liquid surface, the stirring is stopped and the ripple of the liquid surface 55 disappears.
The case where the liquid level 55 is stabilized has been described,
Not limited to this, by providing a wave-eliminating wall (not shown) that surrounds the liquid surface below the ultrasonic sensor 64 in an appropriate range,
The inside surrounded by the wave-eliminating wall can suppress the influence of waves, and can accurately detect the height (B) of the liquid surface even during stirring.

In the above-mentioned embodiment, the case where the specific gravity of the slurry used in the wire saw is detected has been described. However, the specific gravity detecting device shown in FIG. 2 can be widely applied to various uses for detecting the specific gravity of a liquid. it can.

[0023]

As described above, according to the method and apparatus for detecting the specific gravity of the working fluid according to the present invention, from the load detector provided in the container for storing the working fluid and the sensor for detecting the position of the liquid level, Since the specific gravity of the working fluid stored in the container can be automatically detected, it is possible to automatically detect the specific gravity of the working fluid, which conventionally depends on the operator.
The burden on the worker is reduced. Further, the operator is not involved in the detection of the specific gravity, the reliability of the measurement is improved, and the result can be used for various controls, and the stability of the cutting property of the wire saw can be maintained and the wire saw can be maintained. There is an effect that it can correspond to automation of.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a wire saw to which a machining fluid specific gravity detection device according to the present invention is applied.

FIG. 2 is a configuration diagram of a main part of a slurry specific gravity detection device.

[Explanation of symbols]

 10 ... Wire saw 12, 26 ... Wire reel 14 ... Wire 22A, 22B, 22C ... Grooved roller 42 ... Semiconductor ingot (workpiece) 52 ... Slurry storage tank (container) 54 ... Slurry (processing liquid) 55 ... Slurry liquid level 64 ... Ultrasonic sensor 70 ... Load cell (load detector) 72 ... Arithmetic device

Claims (2)

[Claims] 1. A wire row is formed by winding a wire that reciprocates between a pair of wire reels around a plurality of grooved rollers, and a work liquid is supplied to the wire row while supplying a working liquid containing abrasive grains. In a wire saw that cuts the workpiece into a large number of wafers by pressing, a load detector is provided in a container that stores the working liquid, and the weight of the working liquid stored in the container is measured by the load detector. In addition, the sensor detects the position of the liquid surface of the working liquid stored in the container, and the arithmetic unit determines the correspondence between the position of the liquid surface of the container and the volume of the working liquid stored at that time. The weight detected by the load detector and the position detected by the sensor are input to the arithmetic unit in advance, and the container is calculated by the arithmetic unit from the liquid level position detected by the sensor and the correspondence. Stored in Working fluid density detection method characterized in that there working fluid obtains the volume of, and calculates the density value of the machining fluid based on the weight detected and the determined volume with the load detector. 2. A wire row is formed by winding a wire that reciprocates between a pair of wire reels around a plurality of grooved rollers, and a work fluid is supplied to the wire row while a working fluid containing abrasive grains is supplied to the workpiece. In a wire saw that cuts the workpiece into a large number of wafers by pressing, a load detector that is provided in a container that stores the processing liquid and that detects the weight of the processing liquid stored in the container; A sensor for detecting the position of the liquid surface of the stored machining fluid, and the load detector and the sensor are connected, and the correspondence relationship between the position of the liquid surface of the container and the volume of the machining fluid stored at that time is shown. It has a storage unit that is stored in advance, and calculates the volume of the working fluid stored in the container from the relationship between the position of the liquid surface detected by the sensor and the correspondence, and the weight detected by the load detector and the calculation. Volume A machining fluid specific gravity detecting device comprising: a computing device that calculates a specific gravity value of the machining fluid based on the above.