JP2000108010A - Cutting method for wire saw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the warping of a workpiece to be cut or the waviness of a cut surface, and improve the surface roughness of the cut surface of the workpiece. SOLUTION: In a reciprocatively traveling wire saw for cutting an ingot 32 into many thin platelike wafers by winding a traveling wire 14 on a groove roller having plural grooves to form a wire row, and thereto pressing the ingot 32 that is a workpiece while supplying working liquid to the wire row; since the ingot 32 is made to be cut by a setting wire tensile force in a portion for contributing cutting 40 (N) or more, and 1800 (N/mm2) or more in tension, or a breaking load of the wire 14 of 50% or more; the vibration of the wire 14 forming the wire row can be reduced. Consequently a wire row interval Cw can be stabilized to finish the warping of the wafer that is a cut surface of the surface waviness or roughness into a proper condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a wire saw, and more particularly to a method for cutting a wire saw for appropriately setting a wire tension condition of a portion contributing to cutting a workpiece.

[0002]

2. Description of the Related Art In a wire saw, a workpiece is pressed against a traveling wire, and a working fluid containing abrasive grains is supplied to a contact portion between the wire and the workpiece, so that the workpiece is wrapped by the wire. It is a device for cutting. The running wire is wound around a grooved roller having a plurality of grooves to form a row of wires so that the wire always travels in a fixed place, and a tension of about 25 (N) is applied to the wire used for cutting. It was cut by applying voltage. This tension was about 30% of the breaking load of the wire itself.

[0003] If the wire tension in the portion contributing to the cutting is low, the distance between the running wire rows is disturbed, which greatly affects the processing surface accuracy of the wafer to be cut. As a wire running method of a wire saw, a method of feeding a wire from one wire reel and winding the wire as it is on the other wire reel (one-way feed method), or a method of moving the wire fed from one wire reel while reciprocating the other wire is used. There are two methods, a method of winding on a reel (bidirectional feed method).

[0004]

However, since the wire row during the cutting process is subjected to the spraying of the working fluid and various external forces accompanying the cutting process, the wire tension of the portion contributing to the cutting must be sufficiently high. There has been a problem that the interval between the wire rows is not stable, such as the vibration of the wires traveling at high speed. If the wire row spacing is not stable in this way, the thickness of the cut wafer will vary depending on the location, and this will cause a decrease in the cutting accuracy of the wafer such as warpage of the wafer and an increase in the amount of undulation of the cut surface. .

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for cutting a wire saw, which can obtain a high-quality wafer by appropriately setting cutting conditions for wire tension. And

[0006]

According to the present invention, in order to achieve the above object, a running wire is wound around a groove roller having a plurality of grooves to form a wire row, and a machining fluid is applied to the wire row. The tension of the wire is set to 40 (N) or more and the stress is set to 1800 (N / mm ² ) or more in a wire saw that cuts a large number of thin wafers by pressing an ingot as a workpiece while supplying the wafer. To cut the wire, or 5 times the breaking load of the wire.
It is characterized in that it is set to 0% or more for cutting.

According to the present invention, the wire tension is reduced to 40
(N) or more, 1800 (N / mm) ^Two) Or more
And the breaking load of the wire
It was set to 50% or more of
The run-out of the wires forming the thread array is reduced. Therefore,
Stable wire spacing, warped and cut wafer
To obtain high-quality wafers because the amount of undulation is reduced
Can be.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for cutting a wire saw according to the present invention will be described below with reference to the accompanying drawings. First, the overall configuration of the reciprocating traveling wire saw will be described. As shown in FIG. 1, a wire 14 fed from one wire reel 12 </ b> A has guide rollers 16, 1.
Are wound around three groove rollers 18, 18, 18 through a wire running path formed by 6,. A large number of grooves are formed at a constant pitch on the outer peripheral portions of the three groove rollers 18, 18, and 18, respectively. The wire 14 is wound around the grooves of the groove roller 18 in parallel to form a parallel wire. Form row 20. The wire 14 forming the wire row 20 passes through the other wire running path formed symmetrically with respect to the three groove rollers 18, 18, 18 and the other wire reel 12.
B is wound up.

Here, the pair of wire reels 12A,
Motors 22A and 22B are connected to the motor 12A, respectively. The motors 22A and 22B are driven in synchronization with the motor 23 so as to suppress fluctuations in the positions of the dancer rollers 26A and 26B. Reciprocate between the wire reels 12A and 12B at a high speed and stably.

The wire running paths formed on both sides of the wire row 20 have wire guiding devices 24A and 24A, respectively.
B, dancer rollers 26A and 26B are provided. The wire guide devices 24A and 24B are connected to the wire reel 12A,
The dancer rollers 26A and 26B, which guide the wire 14 at a constant pitch from 12B and are driven in synchronization with the motors 22A and 22B, respectively, have weights 27A and
A predetermined tension is applied to the wire 14 on which the wire 7B is suspended and travels. Changing the wire tension is achieved by changing the mass of the weights 27A and 27B.

Above the wire row 20, a wire row 2
A work feed table 30 that moves up and down perpendicular to 0 is installed. Ingot 32 to be processed
Is held at the lower part of the work feed table 30. In the wire saw 10 configured as described above,
Cutting of the ingot 32 is performed by pressing the ingot 32 against the wire row 20 traveling at a high speed. On this occasion,
A slurry is supplied to the wire row 20 from a slurry tank (not shown) via slurry injection nozzles 34, 34,
The ingot 32 is cut into wafers by a lapping action of abrasive grains contained in the slurry.

For cutting, the work feed table 30 is driven to lower the ingot 32, and the ingot 32 is pressed against the traveling wire row 20. FIG. 2 is an explanatory diagram of the wire spacing that affects the accuracy of the cut surface of the wafer.
As shown in FIG. 2, the cutting accuracy of the wafer, which is the subject of the present invention, depends on the wire row interval Cw of the running wire row, and the warpage or cutting of the wafer is changed by the amount of the change in the wire row interval Cw. The amount of undulation on the surface increases, and the cutting accuracy of the wafer also deteriorates.

Factors that change the distance Cw between the running wire arrays include a decrease in the wire diameter due to wear of the wire itself, a variation in wire diameter due to uneven wear of the wire itself, and a run-out of the running wire itself. In order to reduce the amount of wear and uneven wear of the wire, it is preferable to use a wire having a high hardness, a wire having a hardness distribution, particularly a wire having a uniform hardness distribution in a wire cross section, or a wire having a high tensile strength.

Generally, the hardness of the wire has a distribution shown in FIG. The hardness of the wire increases as the distance dw from the center of the wire increases for reasons of wire fabrication. Conversely, the closer to the center, the lower the hardness and the softer. Therefore, when the outer circumference of the wire is worn by abrasive grains during cutting,
The wire surface hardness of the worn portion is reduced, and the wear is further promoted. Due to the characteristic that the hardness of the wire decreases as it approaches the center of the wire, uneven wear tends to occur on the wire during cutting. In FIG. 3, the hardness difference between the outer peripheral portion of the wire (A) and the central portion of the wire is represented by dHa.
However, as shown in FIG. 3, for example, a wire of a type having higher physical properties as compared with (A), such as a wire (B), and having a hardness at the outer circumference of the wire and a hardness at the center of the wire. The smaller the difference of the wire, the smaller the amount of wear and the amount of uneven wear. Therefore, when cutting with a wire saw, it is possible to obtain a wafer with a good amount of warpage or surface undulation of the cut surface.

Next, the warpage and surface roughness of the wafer according to the present invention will be described.
An example of a method for suppressing the amount of torsion will be described. FIG.
FIG. 4 is a diagram showing a relationship between ear tension and wafer warpage.
As shown in FIG. 4, the warpage of the wafer is caused by the tension of the wire.
Show different values. In particular, if the wire tension is 40
When it exceeds N, the effect on wafer warpage is almost one.
It will be fixed. Therefore, if the wire tension is 40 (N) or more,
1800 (N / mm^Two) By setting above
This suppresses lateral deflection during wire running, and reduces wire running.
Stable, good warp with small amount of warpage and cut surface undulation
You can get a wafer. In addition, increase the wire tension.
Doing so may break the wire.
Is about 40-55 (N) and stress is 1800 (N /
mm ^Two) Degree is preferred.

In order to change the wire tension, a weight 27 attached to the dancer rollers 26A and 26B shown in FIG.
This is achieved by changing the masses of A and 27B, and can be appropriately set by measuring the tension of the wire wound around and sent to the groove roller. Further, the object of the present invention can be achieved even by using a method of appropriately controlling only the wire tension at the cut portion by independently controlling the rotating torque of each rotating groove roller.

FIG. 5 is a diagram showing a relationship between a wire tension-breaking load ratio at a portion contributing to cutting and a TTV value indicating a warpage of a wafer. As shown in FIG. 5, the TTV value indicating the warpage of the wafer (the difference between the maximum value and the minimum value of the thickness in the flatness application region of the wafer) shows different values depending on the wire tension-breaking load ratio. In particular, wire tension-
When the rupture load ratio exceeds 50%, the effect on the TTV value indicating the warpage of the wafer becomes almost constant and falls below the allowable TTV value required for the wafer. Therefore,
By setting the wire tension to 50% or more of the wire tension-breaking load ratio, the lateral runout during running of the wire is suppressed, and the running of the wire is stabilized, so that a good wafer having a small amount of warpage or undulation of the cut surface can be obtained. Obtainable. In addition,
If the wire tension is too high, the wire may be broken. Therefore, the wire tension is preferably about 50 to 95% of the wire tension-breaking load ratio.

In a conventional loose abrasive wire saw, a working liquid containing loose abrasive particles is sprayed onto a wire row to cut an ingot by a lapping effect of the loose abrasive particles. As described above, in the loose abrasive wire saw, when the tension of the wire is increased, the contact surface pressure between the ingot and the wire at the ingot cutting portion increases, and the working fluid and the free abrasive grains are removed. It becomes difficult to enter the cut portion, and a problem that the cutting performance is deteriorated occurs.

However, in a fixed abrasive wire saw in which abrasive grains are fixed to the wire itself, abrasive grains that contribute to cutting even when the tension of the wire is increased are fixed to the wire.
This is advantageous because the cutting performance of the ingot does not deteriorate. When the tension of the wire is increased, the surface pressure applied to the guide groove of the groove roller or the guide roller with which the wire is in contact increases, so that the wear amount of the groove of the groove roller or the guide roller also increases. Therefore, when increasing the wire tension, the diameter of the groove roller or guide roller should be set large to reduce the surface pressure of the contact portion with the wire, or the material of the contact portion between the groove roller or guide roller and the wire should be reduced. It is necessary to improve the wear resistance by using a synthetic resin material containing glass fiber having high wear resistance.

When the tension of the wire is set to 50% or more of the breaking load of the wire, it is necessary to configure the wire path so as to reduce the variation in the wire tension in the wire path. is there. Various stresses are applied to the traveling wire, such as bending stress when being wound around the guide roller, stress due to acceleration / deceleration during reciprocation of the wire, and stress due to vibration of the wire in the processing part. If the variation in the wire tension in the wire path is large, the stress applied to the wire exceeds the breaking stress of the wire, which causes a problem that the wire is broken during the cutting process.

[0021]

As described above, according to the wire saw cutting method of the present invention, the tension of the wire used for cutting is set to 40 (N) or more and the stress is set to 1800 (N / mm ² ) or more. Since the wire is cut or set at 50% or more of the breaking load of the wire, the amount of warpage and undulation of the wafer can be reduced,
High quality wafers can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a wire running path of a wire saw according to the present invention.

FIG. 2 is an explanatory diagram of a wire interval.

FIG. 3 is a diagram showing a relationship between a distance from a wire center and a wire hardness.

FIG. 4 is a diagram showing the relationship between wire tension and the amount of undulation on the wafer surface.

FIG. 5 is a diagram showing a relationship between a wire tension-breaking load ratio and a TTV value indicating wafer warpage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Wire saw 14 ... Wire 18 ... Groove roller 20 ... Wire row 27A, 27B ... Weight 32 ... Ingot 36 ... Control device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Tago 9-7-1 Shimorenjaku, Mitaka-shi, Tokyo Tokyo Seimitsu Co., Ltd. (72) Inventor Shuichi Tsukada 9-7-1 Shimorenjaku, Mitaka-shi, Tokyo Co., Ltd. Tokyo Seimitsu F-term (reference) 3C058 AA05 AA12 AA14 AA18 AB08 BA06 CB01 CB10 DA03 3C069 AA01 BA06 BB03 BB04 CA04 EA02

Claims (2)

[Claims] 1. A running wire is wound around a groove roller having a plurality of grooves to form a wire row, and an ingot as a workpiece is pressed against the wire row, so that a large number of thin wafers are formed. In a wire saw to be cut, the tension of the wire wound around the groove roller and contributing to the cutting is set to 40 (N) or more, or 180 to the stress.
A method for cutting a wire saw, wherein the cutting is performed at a setting of 0 (N / mm ² ) or more. 2. A running wire is wound around a groove roller having a plurality of grooves to form a row of wires, and an ingot as a workpiece is pressed against the row of wires, so that a large number of thin wafers are formed. A wire saw to be cut, wherein the tension of the wire at a portion contributing to the cutting wound around the groove roller is set at 50% or more of the breaking load of the wire, and the wire saw is cut. Method.