JPH11347910A - High-strength wire for wire saw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the cutting accuracy, the cutting speed and the durability, and to reduce the cutting loss by specifying the tensile strength of a high strength wire for a wire saw. SOLUTION: A high carbon steel wire containing about 0.80-1.10 wt.% carbon is used for a stock in which the tensile strength of a high strength wire for a wire saw is >=3800 MPa. During the patenting processing on a wire of a specified intermediate wire diameter, generation of decarburization and bainite or the like on a surface layer part is prevented as much as possible. During the drawing, the misalignment of a die and the wire is made small to the utmost using a die excellent in the circularity of a hole. A wet drawing method is preferable to ensure the dimensional accuracy and the toughness of the wire. The total drawing reduction of area required to obtain the tensile strength of >=3800 MPa is approximately >=98% when the carbon content is approximately 0.80 wt.%, and approximately 97% when the carbon content is approximately 0.90 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire for a wire saw used for cutting a hard material such as a single crystal silicon ingot.

[0002]

2. Description of the Related Art A wire saw performs cutting while supplying a cutting fluid containing abrasive grains such as diamond grains and silicon carbide grains while pressing a wire against an object to be cut.
Since the wire used for the wire saw is required to have strength capable of withstanding the tension applied at the time of cutting, a hard steel wire, a piano wire, and the like obtained by drawing a high carbon steel wire are widely used.

Conventionally, a wire for a wire saw using a high-carbon steel wire has been subjected to a patenting process after drawing a high-carbon steel wire such as SWRS80A to a predetermined intermediate wire diameter, and further about 95 to 98%. It is manufactured by wire drawing. And the tensile strength is about 3000-350
It is about 0 MPa.

[0004]

The improvement required for the wire saw includes an improvement in cutting accuracy, an improvement in cutting speed, a reduction in cutting margin loss, and the like. However,
When a conventional wire saw wire is used, it is difficult to improve them simultaneously. For example, it is desirable to use a thinner wire in order to reduce the cutting margin loss, but since the breaking strength of the wire is reduced, it is necessary to reduce the tension applied to the wire during cutting. For this reason, problems such as a decrease in cutting accuracy due to the vibration of the wire and a decrease in cutting speed due to a decrease in the pressure applied to the workpiece are caused.

[0005] Further, since the wire is cut while being moved while being pressed against the object to be cut, the wire is worn and eventually cannot withstand the tension required for cutting. For this reason, the conventional wire saw wire has been limited to repeated use two to three times.

Accordingly, an object of the present invention is to improve the cutting accuracy, the cutting speed, the cutting loss, the durability, etc. at a higher level than in the prior art. It is to provide a strength wire.

[0007]

In order to achieve the above-mentioned object, the high-strength wire for a wire saw according to the present invention is characterized in that the tensile strength is 3800 MPa or more, and the material is preferably It is a high carbon steel containing 0.80 to 1.10% by weight of carbon, and has a pearlite structure that has been drawn.

The cross-sectional shape of the high-strength wire for a wire saw of the present invention is 0.05 to 0.25 mm in diameter and 2 μm in diameter difference.
Preferably, it is less than circular. Here, the diameter difference is the difference between the maximum diameter and the minimum diameter in the same cross section. Further, it is preferable that the length is 300,000 m or more and the diameter difference in the longitudinal direction is less than 2 μm.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In order to obtain a tensile strength of 3800 MPa or more, which is a feature of the high-strength wire for a wire saw of the present invention, it is preferable to manufacture the wire by the following method. (1) A high carbon steel wire containing 0.80 to 1.10% by weight of carbon is used as a material. (2) In applying a patenting treatment to a wire having a predetermined intermediate wire diameter, decarburization of the surface layer, generation of bainite, and the like are prevented as much as possible, and a uniform pearlite structure is formed. (3) In wire drawing, a wire having good roundness of a hole is used, and wire misalignment between the die and the wire is minimized.

As a drawing method, a dry drawing method can be applied, but in order to secure the dimensional accuracy and toughness of the wire, it is preferable to use a wet drawing method in which the wire is drawn in a liquid lubricant. At this time, in order to improve the lubricity, the surface of the patented wire was treated with
It is also preferable to provide a brass plating layer of less than. In addition, 3
The total wire-drawing reduction in area required to obtain a tensile strength of 800 MPa or more varies depending on the composition of the high-carbon steel wire as a material, but is approximately 9 when the carbon content is about 0.80% by weight.
More than 8% and about 97% or more when the carbon content is about 0.90% by weight. The final wire diameter is 0.1 mm.
It is preferable to set it to 05 mm to 0.25 mm.

The above manufacturing method is preferred for the following reasons. First, the reason why a high-carbon steel wire containing 0.80 to 1.10% by weight of carbon is used is that compatibility between workability and strength is high. In particular, the carbon content is 0.85
-0.95% by weight, more preferably 0.1-
It is also preferable to contain about 0.5% by weight of Cr as an alloy element. Then, by forming a uniform pearlite structure in the patenting treatment, good wire drawing workability and work hardening characteristics can be obtained.

Further, by using a die having a good roundness of the hole and drawing the wire while minimizing the misalignment between the die and the wire, a wire having the following characteristics suitable as a wire saw wire can be obtained. Obtainable. (1) Since a portion where strain is locally concentrated on the peripheral surface of the wire is prevented from being generated at the time of drawing and the toughness is impaired, the wire has sufficient toughness to withstand repeated bending by a guide pulley of a wire saw. Is obtained. The decrease in toughness due to strain concentration during wire drawing can be detected by a torsion test or the like, and the amount of torsion that can be given before the wire cracks is 20 times or more per 100 times the wire diameter. preferable. (2) A wire having good roundness and high cutting accuracy can be obtained. Since the roundness of the wire directly affects the cutting accuracy, the cross-sectional shape of the wire as a product has a deviation of 2 μm.
Preferably, it is less than circular. (3) Since dies are not easily reduced at an early stage, a wire having a uniform shape in the longitudinal direction can be obtained even when the die is manufactured continuously over a long length. The preferred length of the wire as a product is 300,000 m or more, more preferably 500,000 m
000 m or more. And it is preferable that there is no weld portion or the like in the middle and that it is uniform, and the difference in diameter in the longitudinal direction is less than 2 μm. Since the wire for a wire saw of the present invention has a high tensile strength, the allowable wear amount when used under the same conditions as the conventional wire is larger than that of the conventional wire. For this reason, it is possible to obtain an effect of reducing the number of wire replacement steps, which is more than the effect of simply increasing the wire length. (4) Further, since the straightness is improved, the wiring work can be easily performed even on a multi-wire saw that cuts a large number of wafers at the same time.

[0013] The final wire diameter is 0.05mm to 0.
The reason why the thickness is set to 25 mm is because high strength and sufficient toughness can be relatively easily achieved at the same time.
That is, in the case of a wire having a diameter exceeding 0.25 mm and a tensile strength of 3800 MPa or more, the wire diameter is 1 mm.
It is difficult to obtain a twist test value of 20 times or more per 00 times. On the other hand, if the wire diameter is less than 0.05 mm, the strength and toughness are likely to be reduced due to the influence of nonmetallic inclusions and the like. In addition, the diameter is 0.05 mm to 0.25 mm
The wire can be suitably used, for example, for cutting out a silicon wafer for manufacturing a semiconductor.

The wire for a wire saw according to the present invention has a tensile strength of 3800 MPa or more, and a particularly preferred range of the tensile strength of the wire is 4000 MPa.
It is not less than 4500 MPa. The reason is that by setting the tensile strength to 4000 MPa or more, more remarkable effects can be obtained on the improvement of cutting accuracy, the cutting speed, the reduction of cutting margin loss, and the improvement of durability.
This is because, if it exceeds, the toughness tends to decrease.

[0015]

EXAMPLES Examples of the wire for a wire saw according to the present invention are shown in Table 1 together with comparative examples. Tensile strength and breaking strength are
It was measured in accordance with JIS Z2241. The average diameter and the diameter difference were measured using a laser wire diameter measuring device having a nominal accuracy of 0.1 μm. The difference between the average diameter near the wire drawing start portion and the average diameter near the wire drawing end portion was defined as the longitudinal diameter difference.

The wire of Example 1 has the same wire diameter as the wire of the comparative example, but has a tensile strength 15% more than that of the comparative example. The wire withstands higher tension and enables an improvement in cutting speed. I do. Further, when the wire is used with the same tension as the wire of the comparative example, greater wear is allowed, and the wire can withstand repeated use twice or more as compared with the wire of the comparative example. For this reason, cutting cost and wire replacement man-hours related to the wire can be significantly reduced.

The wire of Example 2 is a wire that realizes the same breaking strength as the wire of Comparative Example with a smaller diameter. Since the cutting margin loss can be reduced without lowering the cutting speed and cutting accuracy, for example, a larger number of silicon wafers can be cut out from a silicon ingot of the same size.

The wire of Example 3 has a higher breaking strength and a smaller diameter than the wire of Comparative Example.
It is possible to simultaneously improve the cutting speed, improve the cutting accuracy, improve the durability, and reduce the cutting margin loss.

[0019]

[Table 1]

In the patenting treatment at the time of manufacturing the wires of Examples 1 to 3 and Comparative Example, decarburization, generation of bainite and the like were prevented as much as possible to obtain a uniform pearlite structure. Subsequent to the patenting treatment, a brass plating layer of about 4 g per kg of the wire was formed on the wire surface. For the wire drawing, a wet wire drawing method was applied, and in order to obtain a predetermined tensile strength, wire drawing was performed by setting the total area reduction rate of the wire drawing to a value shown in Table 1 according to each component. Further, using a circular die having a hole diameter difference of less than 1% of the average hole diameter, wire drawing was performed such that the misalignment angle between the die hole and the wire was less than 1 degree. In particular, a final die having a diameter difference of less than 1 μm was used.

The twist values of the wires of Examples 1 to 3 manufactured as described above are lower than the wires of the comparative example, but are 20 times or more per 100 times the wire diameter. The toughness was sufficient for use. No local strain concentration was observed on the peripheral surface of the wire.

[0022]

As described above, the high-strength wire for a wire saw according to the present invention has a higher tensile strength than the conventional wire for a wire saw, so that cutting accuracy, cutting speed, and durability are improved. In addition, it is possible to realize an improvement such as a reduction in cutting margin loss at a higher level than before.

The high-strength wire for a wire saw of the present invention can be applied not only to the single wire as exemplified above, but also to a wire for a wire saw having a structure in which a plurality of strands are twisted. In such a case, an excellent effect can be similarly obtained.

Claims (4)

[Claims] 1. A high-strength wire for a wire saw, having a tensile strength of 3800 MPa or more. 2. The high-strength wire for a wire saw according to claim 1, wherein the material is a high-carbon steel containing 0.80 to 1.10% by weight of carbon, and a metal structure is a drawn pearlite structure. 3. The cross-sectional shape is 0.05 to 0.25 mm in diameter.
The high-strength wire for a wire saw according to claim 1 or 2, wherein the wire has a circular shape with a diameter difference of less than 2 µm. 4. The high-strength wire for a wire saw according to claim 3, wherein the length is not less than 300,000 m and the difference in diameter in the longitudinal direction is less than 2 μm.