Multi-strand combined rotary twisted cutting wire

Abstract

The application discloses a multi-strand combined rotary twisted cutting wire, which comprises two or more tungsten cutting filaments, the multi-strand tungsten cutting filaments are spirally twisted to form a cutting wire, and the outer surface of the cutting wire is provided with a plurality of ring pressure surfaces. The multi-strand tungsten cutting filaments are spirally twisted to form a cutting wire, and the overall tensile strength is greatly improved after the spirally twisted. In the case of the same overall diameter, the tensile strength of the spirally twisted cutting wire is greater than that of the single tungsten cutting filament. From the perspective of raw materials, the application improves the tensile strength of the unit cross section. Furthermore, the outer surface of the cutting wire is provided with ring pressure surfaces, the highest part of the protruding outer surface is compressed to form the ring pressure surfaces, so as to reduce the concave-convex degree of the overall outer surface, reduce the scratches formed on the silicon surface during cutting, and make the surface after cutting more smooth.

Description

Technical Field

[0001] This invention relates to the field of cutting wire technology, and more specifically to a multi-strand combined rotary twisted cutting wire particularly suitable for silicon wafer cutting. Background Technology

[0002] my country will accelerate the industrialization of third-generation semiconductor materials and technologies, represented by silicon carbide and gallium nitride. Silicon carbide applications are ubiquitous and widespread, ranging from daily necessities to industrial manufacturing and military products, with the demand for smart chips reaching astronomical figures. High-end silicon carbide raw material rods for chip production must be cut into thin sheets before use. However, silicon carbide is a very hard and dense semiconductor material, making it extremely expensive, and its cutting speed and efficiency are very low. Currently, the conventional production method is carbon steel wire driven slurry grinding and cutting. Using carbon steel wire as a cutting consumable results in low first-pass yield, slow speed, and surface defects such as striations on the finished product, which cannot fully meet the requirements for precision silicon carbide cutting.

[0003] The inventor previously invented a high-performance rare-earth alloy tungsten cutting wire. The surface of the tungsten cutting wire has a dendritic texture, which improves the bonding force between the metal coating and the tungsten wire, ensuring the consolidation quality of the diamond particles. This extends the service life of the cutting wire while maintaining sufficient tensile strength. For the specific structure, please refer to the Chinese invention patent application filed by the inventor on February 24, 2022, with publication number CN114480936A. This product has received widespread praise from users since its market launch. However, the following areas for improvement still exist during use:

[0004] As silicon wafer prices rise, stricter requirements are placed on the material loss ratio during the dicing process. Experiments have shown that finer dicing wires result in lower material loss, thus necessitating a reduction in the diameter of the dicing wires. However, this reduction in diameter leads to decreased tensile strength and shortened lifespan. Therefore, improvements to the dicing wire design are needed to maintain a certain level of tensile strength while reducing the diameter. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, a multi-strand combined rotary twisted cutting wire with small diameter, high tensile strength, and long service life is provided.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A multi-strand merging and rotating twisted cutting wire includes two or more tungsten cutting filaments, which are spirally twisted together to form a cutting wire. The outer surface of the cutting wire is provided with multiple annular pressing surfaces.

[0008] In this invention, the outer surface of the cutting wire is provided with a spiral-shaped chip removal groove for cutting and chip removal.

[0009] In this invention, the outer surface of the cutting wire is provided with diamond powder particles.

[0010] In this invention, the diameter of the single-strand tungsten cutting filament is between 0.015 mm and 0.15 mm.

[0011] In this invention, the spiral twist angle of a single strand of tungsten cutting filament per centimeter is between 3600° and 7200°.

[0012] In this invention, the cross-section of the cutting wire is circular.

[0013] In this invention, the cross-section of the cutting wire is a regular polygon.

[0014] The beneficial effects of this invention are as follows: This invention forms a cutting wire by spirally winding and twisting multiple strands of tungsten cutting filaments together. After spiral winding and twisting, the overall tensile strength is significantly improved; under the same overall diameter, the tensile strength of the spirally wound cutting wire is greater than that of a single strand of tungsten cutting filament. From the perspective of raw materials, this invention improves the tensile strength per unit cross-section.

[0015] Furthermore, the present invention provides an annular pressing surface on the outer surface of the cutting wire. After spiraling, the highest part of the outer surface is compressed to form an annular pressing surface, thereby reducing the unevenness of the overall outer surface, reducing scratches formed on the silicon surface during cutting, and making the cut surface smoother.

[0016] Furthermore, after multiple strands of tungsten cutting filaments are spirally wound and twisted together, chip removal grooves are left between adjacent filaments. These grooves not only facilitate the flow of chips during cutting and reduce scratches on the silicon surface, but also play a role in heat dissipation, lowering the temperature generated during cutting. In a slurry cutting environment, this allows for a greater slurry flow, thereby increasing the cutting speed. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0018] Figure 1 This is a schematic diagram of the structure of Embodiment 1;

[0019] Figure 2 This is a top view of Embodiment 1;

[0020] Figure 3 This is a schematic diagram of the structure during processing in Example 1;

[0021] Figure 4 for Figure 3 A schematic diagram of the processing mold in the diagram;

[0022] Figure 5 This is a schematic diagram of the structure of Example 2;

[0023] Figure 6 This is the front view of Embodiment 2;

[0024] Figure 7 This is a top view of Example 2. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "left," "right," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] Example 1:

[0029] Reference Figures 1 to 4This embodiment provides a multi-strand merging and rotating twisted cutting wire, comprising two or more tungsten cutting filaments 1, which are spirally twisted together to form the cutting wire. The outer surface of the cutting wire has multiple annular pressing surfaces 2. In this embodiment, the tungsten cutting filaments 1 are configured as three strands, and the overall diameter of the cutting wire is twice that of a single strand of tungsten cutting filament 1. The diameter of a single strand of tungsten cutting filament 1 is between 0.015mm and 0.15mm, preferably 0.04mm. After subsequent processing, the overall diameter of the cutting wire is reduced to only 0.075mm. The overall tensile strength and service life are superior to a single strand of tungsten cutting filament with a diameter of 0.075mm, and only half that of existing 0.15mm steel wire. Therefore, the cutting kerf is smaller, the yield is more than 15% higher, and the raw material loss rate is significantly reduced. The current price of a 0.68mm thick silicon carbide wafer is 6,000 yuan per piece. The original loss per slit was 0.15mm, but now the loss per slit is 0.075mm. This allows a single silicon carbide raw material to be cut into several or even a dozen more wafers, resulting in the production of silicon carbide wafers worth an additional 100,000 yuan.

[0030] In this embodiment, the tungsten cutting filament 1 is a high-performance rare-earth alloy tungsten cutting wire. The tungsten cutting filament 1 is made of a material synthesized in a weight percentage ratio of 99.75%-99.15% tungsten and 0.25%-0.85% rare earth, wherein the rare earth contains more than 99.99% lanthanum by weight. The specific molding process and structure can be referred to the Chinese invention patent application filed by the inventor on February 24, 2022, with publication number CN114480936A, which will not be described in detail here.

[0031] In this embodiment, the annular pressing surface 2 is formed by an annular pressing die 4 made of tungsten steel or CVD diamond material, as shown in the attached figure. Figure 3 and Figure 4As shown, the annular die-cutting mold 4 has a cutting hole 40 in the middle. The front section of the cutting hole is an inlet area 41 with a significantly reduced diameter, and the opening angle of the inlet area 41 is 60°~90°. Following the guide area 41 are a lubrication area 42 and a compression area 43 with slightly reduced diameters, and the opening angles of the lubrication area 42 and the compression area 43 are 30°~40° and 12°~24°, respectively. The rear section of the compression area 43 is a sizing area 44 with a constant diameter, and the sizing area 44 is smaller than the diameter of the cutting wire after the three strands of tungsten cutting wire 1 are spirally wound and twisted. Following the guide area 41 are a safety angle 45 with a gradually increasing diameter and an outlet area 46, and the opening angles of the safety angle 45 and the outlet area 46 are 10° and 60°~90°, respectively. During cutting, the annular die-cutting mold 4 needs to be placed in a high-temperature furnace for heating. The temperature inside the furnace is 350°C, and the mold temperature is close to 400°C. The ratio of the diameter after cutting to the diameter before cutting is 84%~92%:1, preferably 92%:1, and the cutting speed is preferably 50~150mm / min. The annular cutting die 4 flattens or removes the highest protruding part of the outer surface, forming an annular pressing surface 2. This ensures the flatness of the entire outer surface of the cutting wire, reduces scratches on the silicon surface during cutting, and makes the cut surface smoother. The finished product has a high surface finish after cutting, is less prone to cutting streaks, reduces the difficulty of grinding and polishing, has a high first-pass yield, and excellent quality, meeting the requirements for high stability, high precision, high quality, and ultra-thin processing.

[0032] Meanwhile, after ring pressing, the three strands of tungsten cutting wire 1 are more tightly spirally wound, resulting in a more robust structure. The high-temperature mold also eliminates internal stress during the spiral winding of the tungsten cutting wire 1, making the internal structure more stable and less prone to deformation. In this embodiment, the cross-section of the cutting hole is circular, and the cross-section of the overall cutting wire after cutting is also circular. Of course, the cross-section of the cutting hole can also be a regular polygon, thus making the cross-section of the overall cutting wire after pressure cutting a regular polygon to cope with different cutting environments.

[0033] In a preferred embodiment, after the three tungsten cutting wires 1 are spirally wound and twisted, a spiral-shaped chip removal groove 3 is left between adjacent tungsten cutting wires 1. This chip removal groove 3 not only facilitates the flow of chips during cutting and reduces scratches on the silicon surface, but also plays a role in heat dissipation, reducing the temperature generated during cutting and ensuring better cutting results. Traditional cutting wires have a smooth surface, so cutting needs to be done in slurry, or diamond powder needs to be added to the surface of the cutting wire. Cutting relies on the flow of slurry, and the greater the slurry flow, the faster the cutting speed. The chip removal groove 3 can drive a greater slurry flow in a slurry environment, and its slurry flow can reach three times that of traditional cutting wires. Cutting a 150mm (6-inch) conventional silicon carbide rod, it takes 7 to 8 days to cut one piece with ordinary carbon steel wire, while the present invention, using the spiral chip removal groove 3, can cut one piece in only half the time. The output and speed are more than 100% higher than the traditional method, with fewer wire breaks, lower equipment failure rate, reduced maintenance frequency, and higher equipment efficiency and utilization.

[0034] When working in a non-mortar environment, tiny diamond powder particles can be placed on the outer surface of the cutting wire to increase the friction on the cutting wire surface, thereby ensuring the cutting effect.

[0035] In this embodiment, the helical twist angle of a single-strand tungsten cutting filament 1 per centimeter is between 3600° and 7200°. That is, three tungsten cutting filaments 1, each one centimeter long, are helically twisted together, with 10 to 20 turns, and so on. When the diameter of the single-strand tungsten cutting filament 1 is 0.02 mm, the preferred helical twist angle per centimeter is 4800°. Here, the smaller the diameter, the larger the helical twist angle. When the diameter is large and the twist angle is small, a good twisting effect cannot be achieved; when the twist angle is too large, it not only leads to an excessively large winding diameter, but also does not significantly improve the tensile strength.

[0036] Example 2:

[0037] Reference Figures 5 to 7 The structure and principle of this embodiment are basically the same as those of Embodiment 1. The difference is that the tungsten cutting wire 1 is set as two strands. After the overall cutting wire is cut by the cutting hole, its diameter is twice that of a single strand of tungsten cutting wire 1. In this embodiment, the diameter of the single strand of tungsten cutting wire 1 is preferably 0.05mm, so that the diameter of the overall cutting wire is only 0.09mm. The overall tensile strength and service life are better than those of a single strand of tungsten cutting wire with a diameter of 0.09mm, and the cutting kerf is finer, which saves more material.

[0038] Furthermore, the present invention is not limited to tungsten wire, but can also be made of other metal materials and have a certain tensile strength, and can be used to form stranded cutting wire using the structure of the present invention.

[0039] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A multi-strand combined rotary twisted cutting wire, characterized in that: It includes two or more tungsten cutting filaments (1), and the multiple tungsten cutting filaments (1) are spirally twisted together to form a cutting wire. The outer surface of the cutting wire is provided with multiple ring-pressing surfaces (2) to reduce the formation of scratches on the silicon surface during cutting. The outer surface of the cutting wire is provided with spiral-shaped chip removal grooves (3) for cutting and chip removal. The annular pressing surface (2) is formed by pressing and cutting with an annular pressing die (4). The annular pressing die (4) flattens or cuts off the part with the highest protrusion on the outer surface of the cutting wire to form the annular pressing surface (2). The annular die (4) has a die-cutting hole (40) in the middle. The front section of the die-cutting hole is an inlet area (41) with a significantly reduced diameter. The opening angle of the inlet area (41) is 60°~90°. After the inlet area (41), there are a lubrication area (42) and a compression area (43) with a slightly reduced diameter. The rear section of the compression area (43) is a sizing area (44) with a constant diameter. After the inlet area (41), there are a safety angle (45) with a gradually increasing diameter and an outlet area (46). During the pressing and cutting process, the annular pressing and cutting mold (4) needs to be placed in a high-temperature furnace for heating. The temperature inside the furnace is 350°C, and the ratio of the diameter after pressing and cutting to the diameter before pressing and cutting is 84%~92%.

2. The multi-strand combined rotary twisted cutting wire according to claim 1, characterized in that: The outer surface of the cutting wire is covered with diamond powder particles.

3. The multi-strand combined rotary twisted cutting wire according to claim 1, characterized in that: The diameter of the single-strand tungsten cutting filament (1) is between 0.015 mm and 0.15 mm.

4. The multi-strand combined rotary twisted cutting wire according to claim 1, characterized in that: The single-strand tungsten cutting filament per centimeter (1) has a spiral twist angle between 3600° and 7200°.

5. The multi-strand combined rotary twisted cutting wire according to claim 1, characterized in that: The cutting wire has a circular cross-section.

6. The multi-strand combined rotary twisted cutting wire according to claim 1, characterized in that: The cross-section of the cutting wire is a regular polygon.

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