JP2014058014A - Wire saw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive-grain-fixed wire saw having good sharpness and less kerf loss.SOLUTION: A wire saw is dispersion-anchored with a grain aggregate on its surface. The grain aggregate consists of main grains in a predetermined grain diameter range functioning as an abrasive grain for grinding a material and auxiliary grains smaller in grain size than the main grains. In a number-based integration distribution of the grain aggregate, the accumulation% of the auxiliary grains is at least 11% of the accumulative grain number from the small-sized side of the number-based integration distribution.

Description

  The present invention relates to a wire saw used for cutting hard materials such as silicon, ceramics, and sapphire.

  Conventionally, this type of wire saw has been used for cutting hard and difficult-to-work materials such as ceramics and stones, as well as silicon wafers for semiconductors and sapphire in LED applications.

  In the past, so-called abrasive-free wire saws that were cut using a slurry containing abrasive and coolant were the mainstream, but abrasive-free wire saws must be cut while supplying the slurry to the sample. The workability was not good because it was necessary. In addition, sludge, which is a mixture of slurry and swarf, is generated during cutting, which not only degrades the working environment but also requires the sample to be washed after cutting to remove the sludge from the sample. There were also environmental and cost inefficiencies.

  In order to solve such problems, an abrasive fixed wire saw has been developed. An abrasive-fixed wire saw has the advantage that the sharpness is extremely good, no slurry is required, contamination of the machine and its surroundings can be reduced, and the working environment can be improved. In addition, since a diamond wire saw having a length of several hundred meters or several tens of kilometers or more can be manufactured, a large number of wafers can be sliced at one time. Cutting speeds several times higher than wire saws can be obtained.

  In recent years, many proposals have been made to improve the performance of such wire-fixed wire saws. For example, the particle diameter of the abrasive grains is kept within a certain range, and the abrasive grains are placed in the core wire. There has been proposed a method for improving the sharpness by making the layer to be dispersed and fixed to a certain thickness (see Patent Document 1). Although it is certain that a sharp wire saw can be obtained in this way, the object to be cut is a delicate part used in precision equipment such as a silicon wafer, so it has a better sharpness and less kerf loss. The reality is that a wire saw is required.

Japanese Patent Application Laid-Open No. 2000-263452

  In view of the circumstances as described above, an object of the present invention is to provide an abrasive-fixed wire saw that is sharper and less kerf than the conventional product.

  As a result of intensive studies to solve such problems, the inventors of the present invention have a wire saw in which the particle group is dispersed and fixed on the surface of the wire, and the particle group has a predetermined particle size that functions as an abrasive for grinding the material. A primary particle in a range and secondary particles having a particle size smaller than the primary particle, and in the number-based cumulative distribution of the particle group, the cumulative percentage of the secondary particles is from the small particle diameter side of the number-based cumulative distribution. By using a wire saw that is 11% or more of the cumulative number of particles, it has been found that it is possible to provide an abrasive-fixed wire saw that is sharper and has less kerf than the conventional abrasive process type wire saw. .

That is, the gist of the present invention is as follows.
[1] A wire saw in which a group of particles is dispersed and fixed on the surface of a wire, and the group of particles includes a main particle having a predetermined particle size range that functions as an abrasive for grinding a material, and a secondary particle having a smaller particle size than the main particle. A wire saw in which the cumulative percentage of the secondary particles is 11% or more of the cumulative number of particles from the small particle diameter side of the number-based cumulative distribution in the number-based cumulative distribution of the particle group,
[2] The wire saw according to [1], wherein the cumulative percentage of the secondary particles is 50% or more of the cumulative number of particles from the small particle diameter side of the number-based cumulative distribution,
[3] The wire saw according to [1] or [2], wherein a median diameter of the sub-particles is 30% or less of a median diameter of the main particles.
[4] The wire saw according to any one of [1] to [3], wherein the secondary particles include at least one selected from diamond, nickel, and a nickel-phosphorus alloy,
[5] The wire saw according to any one of [1] to [4], wherein the wire saw is for cutting a silicon wafer,
[6] The wire saw according to the above [5], wherein the silicon constituting the silicon wafer is polycrystalline.
It is.

  ADVANTAGE OF THE INVENTION According to this invention, compared with the conventional abrasive grain fixed type wire saw, the sharpness and the abrasive grain fixed type wire saw with few kerf loss can be provided.

The external view of the wire saw in this invention. 2 is a number-based particle size distribution and a number-based particle size cumulative distribution curve of abrasive grains in Example 1. FIG. The number-based particle size distribution and number-based particle size cumulative distribution curve of abrasive grains in Comparative Example 1.

  The present invention is a wire saw in which a group of particles are dispersed and fixed to the surface of a wire, and the group of particles has a main particle in a predetermined particle size range that functions as an abrasive for grinding a material, and a particle size smaller than the main particle. The wire saw is composed of secondary particles, and the cumulative percentage of the secondary particles in the number-based cumulative distribution of the particle group is 11% or more of the cumulative number of particles from the small particle diameter side of the number-based cumulative distribution.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a side view showing an embodiment of a wire saw according to the present invention. As shown in FIG. 1, the wire saw 1 in the present embodiment has a configuration in which main particles 13 and sub-particles 14 are dispersed and fixed to a core wire 12 that is a basic skeleton thereof.

  The core wire 12 may be any wire used for a normal wire saw, and is preferably a piano wire, for example, from the viewpoint that it can be easily processed into an ultrafine wire and has sufficient strength. As the material of the piano wire, various metal wires whose strength does not deteriorate due to the melting temperature of the solder can be used, and any one of iron, nickel, cobalt, chromium, tungsten, molybdenum, copper, titanium, aluminum and alloys thereof The one consisting of is preferred. In particular, those made of high carbon steel including piano wire are preferable in that they can be obtained inexpensively and stably, and the cost can be reduced. In addition, a single wire or a stranded wire of any one of carbon fiber, aramid fiber, boron fiber, and glass fiber may be used other than the piano wire. The diameter of the core wire 2 is preferably 50 to 200 μm.

  When a particle size distribution curve of a particle group dispersed and fixed to the wire saw 1 is created, the particle group is roughly divided into a main particle 13 and a sub particle 14 depending on the particle diameter. The particle diameter of the main particles 13 is preferably in the range of 5 to 60 μm, and the median diameter is preferably 8 to 50 μm. On the other hand, the particle diameter of the secondary particles 14 is preferably in the range of 0.1 to 3 μm, and the median diameter is preferably 0.5 to 2 μm. And in the relationship between the median diameter of the main particles 13 and the median diameter of the sub-particles 14, the median diameter of the sub-particles 14 is 30% or less, more preferably 15% or less, more preferably 8% of the median diameter of the main particles 13. % Or less is recommended.

  The main particles 13 function as abrasive grains when cutting an object to be cut such as silicon. On the other hand, the secondary particles 14 do not directly contribute to the cutting itself, but by increasing the surface area of the wire saw and forming irregularities on the surface of the wire saw, the carry amount of the coolant used at the time of cutting is increased. This is thought to contribute to improving the sharpness of the wire saw and reducing kerf loss.

  The cumulative number of particles from the small particle diameter side of the sub-particles 14 may be 11% or more, and more preferably 40% or more with respect to the number of particles of the entire abrasive grains. By doing so, it is possible to obtain a wire saw having a better sharpness and less kerf loss than a conventional wire saw.

  The main particles 13 have a configuration in which a so-called superabrasive such as diamond or CBN is coated with a metal film of nickel or a nickel-phosphorus alloy. On the other hand, the secondary particles 14 may have the same configuration as the main particles 13, may be diamond, CBN, nickel, nickel-phosphorus alloy, or a mixture thereof.

  When the particle group consisting of the main particles 13 and the sub-particles 14 is dispersed and fixed to the core wire 12, it is dispersed and fixed by a conventionally known method such as a method using a resist bond, a method using electrodeposition, or a method using brazing. However, the present invention is not limited to this as long as it has a sufficient holding power for abrasive grains when used as a wire saw.

  At this time, the main particles 13 and the sub-particles 14 may be separately dispersed and fixed to the core wire 12. However, from the viewpoint of reducing the number of steps, it is desirable to mix and fix both particles. However, it is necessary to disperse and fix the main particles 13 and the sub-particles 14 to the entire core wire without any deviation regardless of the procedure.

  The wire saw thus obtained has good sharpness and little kerf loss, and is suitable for thinly cutting a high-hardness member.

  For example, in order to obtain a silicon wafer necessary for manufacturing a solar cell panel or a semiconductor, it is necessary to thinly cut a hard ingot made of silicon crystals, and the wire saw according to the present invention is used for such a use. Is possible. In general, single crystalline silicon can be obtained with high performance when a solar cell or a semiconductor is manufactured. However, in recent years, with an increase in demand for solar cell panels having a large area, in order to obtain a silicon wafer at a low cost, a silicon wafer is often obtained from an ingot made of polycrystalline silicon. The wire saw according to the present invention is suitable not only for cutting an ingot made of monocrystalline silicon but also for cutting an ingot made of polycrystalline silicon.

  Hereinafter, based on an Example, Embodiment of this invention is described more concretely, This invention is not limited to these.

Example 1
Nickel fine powder was added to nickel-coated diamond abrasive grains to obtain a particle group for dispersing and fixing to the surface of the wire saw core wire. When the particle group was subjected to measurement of the number-based particle size distribution using a flow type particle group analyzer, a number-based particle size distribution having two peaks of main particles and sub-particles was obtained as shown in FIG. It was. Thereafter, the particle group was dispersed and fixed to the core wire to obtain a wire saw.

(Comparative Example 1)
By a method similar to that in Example 1, a particle group for dispersing and fixing to the surface of the wire saw core wire was obtained on the nickel-coated diamond abrasive grains. Then, when the number-based particle size distribution was measured by the same method as in Example 1, as shown in FIG. 3, the number-based particle size having only one peak due to the main particles mainly having a particle size of 10 μm or more. A distribution was obtained. Thereafter, a wire saw was obtained in the same manner as in Example 1.

(Evaluation 1: Surface roughness evaluation test)
Using the wire saws of Example 1 and Comparative Example 1, a polycrystalline silicon wafer was cut, and the surface roughness of the cut surface was measured using a surface roughness measuring instrument manufactured by Tokyo Seimitsu Co., Ltd. (model number: Surfcom 1500D × 3), the center average roughness Ra and the ten-point average roughness Rz were measured and calculated. In addition, Ra value and Rz value of three places were measured from one cut surface obtained by each wire saw of Example 1 and Comparative Example 1, and the average value was calculated.

  As shown in Table 1, the surface roughness of Example 1 was lower in both Ra value and Rz value than the surface roughness of Comparative Example 1. In Example 1, this means that the surface of the cut surface has less irregularities, and it can be seen that the wire saw smoothly cut the silicon wafer during cutting, suggesting the sharpness of the wire saw. It is believed that there is. In addition, the fact that the surface of the cut surface has less unevenness is considered that the wire saw has moved without being displaced from the cutting direction, and the kerf loss during cutting is also suppressed as much as possible.

1. Wire saw 12, core wire 13, main particle 14, sub-particle

Claims (6)

  A wire saw in which a group of particles is dispersed and fixed to the surface of a wire, and the group of particles includes a main particle having a predetermined particle size range that functions as an abrasive for grinding a material, and sub-particles having a particle size smaller than the main particle. Thus, in the number-based cumulative distribution of the particle group, the cumulative percentage of the secondary particles is 11% or more of the cumulative number of particles from the small particle diameter side of the number-based cumulative distribution.   The wire saw according to claim 1, wherein the cumulative percentage of the secondary particles is 50% or more of the cumulative number of particles from the small particle diameter side of the number-based cumulative distribution.   The wire saw according to claim 1 or 2, wherein a median diameter of the secondary particles is 30% or less of a median diameter of the main particles.   The wire saw according to any one of claims 1 to 3, wherein the secondary particles include at least one selected from diamond, nickel, and a nickel-phosphorus alloy.   The wire saw according to any one of claims 1 to 4, wherein the wire saw is for cutting a silicon wafer. The wire saw according to claim 5, wherein the silicon constituting the silicon wafer is polycrystalline.

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