JP2014172115A - Fixed abrasive grain wire, and method for production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixed abrasive grain wire favorable in cutting sharpness from the initial stage of cutting process and excellent in processing efficiency and processing accuracy.SOLUTION: A fixed abrasive grain wire 10 is provided with: a metallic wire 11 having ductility; diamond abrasive grains 14 which are one type of super-abrasives made by temporarily fixing a part of a conductive covering layer 12 formed on a part of a surface to the outer peripheral surface of the wire 11 in a closely contacting state by a first electrodeposition layer 13; and a second electrodeposition layer 15 covering the electrodeposition layer 13 on the outer peripheral surface of the wire 11 and the covering layer 12 of the diamond abrasive grains 14 in order to fix the diamond abrasive grains 14 to the outer peripheral surface of the wire 11. The covering layer 12 is composed of Ni, and the first and second electrodeposition layers 13 and 15 are each formed by nickel plating.

Description

  The present invention relates to a fixed abrasive wire used for slicing a crystalline material such as a solar cell, semiconductor silicon, a magnetic material, sapphire, and SiC.

  Fixed abrasive wires used when slicing a silicon ingot or the like include a resin wire in which abrasive grains are fixed by a resin bond and an electrodeposition wire in which abrasive grains are fixed by electrodeposition. The resin wire has a good surface roughness and the like, and has a high processing accuracy, but has a problem that the processing efficiency is inferior to that of an electrodeposited wire. On the other hand, the electrodeposition wire has higher processing efficiency than the resin wire, but has a problem that the surface roughness of the cut surface is poor, and it takes a long time to manufacture and the cost is high.

  As what solves such a problem, there exists a fixed abrasive wire described in patent documents 1-3, for example. These fixed-abrasive wires increase the production speed by fixing abrasive grains, which are coated on the entire surface with metals such as Ni and Cu, and carbides such as TiC and SiC, to the outer surface of the wire by electrodeposition. is there.

  On the other hand, the applicant of the present invention temporarily attached the electrode having a conductive wire at least on the surface and an electrodeposition layer in a state where a part of the conductive coating layer formed on a part of the surface is in close contact with the outer peripheral surface of the wire. Proposed fixed abrasive wire with a superabrasive grain and a synthetic resin layer covering the outer electrode electrodeposition layer and the superabrasive coating layer to fix the superabrasive grain to the outer periphery of the wire (For example, refer to Patent Document 4).

JP 2006-181698 A JP 2004-27283 A JP 2006-181701 A JP 2011-16208 A

  Since the fixed abrasive wire described in Patent Documents 1 to 3 is manufactured by forming an electrodeposited metal layer on a coating layer formed over the entire surface of the abrasive grain, it is exposed from the electrodeposited metal layer. The other abrasive grains adhere to the coating layer on the surface of the polished abrasive grains and aggregate the abrasive grains in the length or radial direction of the wire. The outer diameter of the fixed abrasive wire as the final product and the tip height of the abrasive grains There is a tendency for the variation of the to become large.

  When the agglomerated portion of the abrasive grains increases, the torsional strength of the wire that is the core wire decreases, and the breakage of the fixed abrasive wire is likely to occur. Moreover, since there is an electrodeposition layer on the surface layer of the abrasive grains, it is difficult to cut into the work material and the processing efficiency is low. For this reason, there is a problem that not only the silicon wafer, which is a work material, is warped and the thickness variation is increased, but also the surface roughness of the cut surface is deteriorated and the processing accuracy is lowered. In addition, the electrodeposition layer at the tip of the abrasive grains may come into contact with the work material, and the work material such as a wafer may be contaminated with metal.

  Therefore, if the coating layer and the electrodeposition layer on the surface of the abrasive grains are to be removed in order to improve the cutting into the work material, the removal work requires a lot of labor and time, leading to an increase in cost. .

  Moreover, since the fixed abrasive wire described in Patent Document 3 is fixed to the electrodeposited metal layer with the coating layer formed on the surface of the abrasive grain, the abrasive grains exposed from the electrodeposited metal layer in a later step An operation for removing the coating layer on the surface is necessary, and this removal operation requires a lot of time. In addition, other abrasive grains adhere to the coating layer on the surface of the abrasive grains exposed from the electrodeposited metal layer, resulting in aggregation of the abrasive grains.

  On the other hand, the fixed abrasive wire described in Patent Document 4 is excellent in that the occurrence of disconnection during slicing is small, but there is a surface that is not sharp enough depending on the type of workpiece.

  The problem to be solved by the present invention is to provide a fixed abrasive wire that has good sharpness from the initial stage of cutting and is excellent in processing efficiency and processing accuracy.

  The fixed-abrasive wire of the present invention includes a flexible wire having at least a surface having conductivity and a part of a conductive coating layer formed on a part of the surface in contact with the outer peripheral surface of the wire. A superabrasive grain temporarily fixed by an electrodeposition layer, and a first electrodeposition layer on the outer peripheral surface of the wire and a coating layer of the superabrasive grain for fixing the superabrasive grain to the outer peripheral surface of the wire. And a second electrodeposition layer.

  With such a configuration, the superabrasive grains fixed to the outer peripheral surface of the wire have a portion where the coating layer is in close contact with the outer peripheral surface of the wire, and there is no coating layer at the tip portion in contact with the workpiece. Since the substance constituting the superabrasive grains is exposed, the sharpness is improved and excellent processing accuracy is obtained. In addition, since the superabrasive grains in which the constituent materials are exposed directly bite into the workpiece during processing, the sharpness is good from the initial stage of cutting and the processing efficiency is also good. Superabrasive grains refer to hard granular materials such as diamond and cBN. The superabrasive coating layer is preferably formed of Ni, Cu, TiC, SiC, or the like.

  Here, if the coating layer is formed on the specific crystal surface of the superabrasive grains, the crystal orientation of the superabrasive grains can be aligned because the coating layer is adhered and fixed to the outer peripheral surface of the wire. The wear rate of the superabrasive grains can be made uniform. In addition, since the sharpness reduction rate due to the wear of the superabrasive grains is alleviated, the tool life is extended, which is effective for cost reduction. In this case, it is desirable to form a coating layer on the 100 or 111 plane which is the specific crystal plane of the superabrasive grain, but there is no problem even if a coating layer is formed on the crystal plane adjacent to the 100 or 111 plane. Absent.

  On the other hand, it is desirable to form the coating layer in a region of 20% to 80% of the surface area of the superabrasive grains. With such a configuration, the electrodeposited layer is formed in the region of 20% to 80% of the surface area of the superabrasive grains, so that the constituent material of the superabrasive grains is exposed in the remaining 80% to 20% regions. Therefore, the sharpness is improved, and excellent processing efficiency and processing accuracy are exhibited.

  When the area of the coating layer is less than 20%, the adhesive force of the superabrasive grains to the second electrodeposition layer is insufficient, and the abrasive grains fall off during the processing. The abrasive coating layer is exposed from the second electrodeposition layer, the superabrasive grains agglomerate, or the superabrasive grains to which the coating layer adheres come into contact with the work material (wafer, etc.) The above range is preferable because it causes metal contamination.

  Moreover, if the thickness of the coating layer is in the range of 2 μm to 20 μm, a strong fixing force to the second electrodeposition layer can be obtained, and the wire diameter after fixing the abrasive grains can be made uniform. In addition, when the thickness of the coating layer is less than 2 μm, the adhesion to the first electrodeposition layer becomes weak, and superabrasive grains may fall off during cutting. When the thickness exceeds 20 μm, the second electrodeposition layer The above range is suitable because the growth of the plating is promoted and the superabrasive grains are buried in the second electrodeposited layer or the wire diameter of the fixed abrasive wire is increased.

  Next, the method for producing a fixed abrasive wire according to the present invention includes a step of forming a conductive coating layer on a part of the surface of the superabrasive grain, and the outer peripheral surface of a flexible wire having at least a surface conductivity. A step of temporarily adhering the superabrasive grains to the outer peripheral surface with a first electrodeposition layer in a state in which a part of the layer is in close contact; and an electrodeposition layer on the outer peripheral surface of the wire and a coating layer of the superabrasive grains And a step of coating with an electrodeposition layer.

  With this configuration, the portion covered with the superabrasive coating layer is fixed to the outer circumferential surface of the wire with the electrodeposition layer in a posture facing the inner side (wire axis side) and is not covered with the coating layer. A fixed abrasive wire having a portion exposed to the outside is formed. As a result, during the cutting process, the exposed portion of the superabrasive grains is directly contacted with the work piece and cutting is performed, so that the fixed abrasive grains have good sharpness from the initial stage of the cutting process, and have excellent processing efficiency and processing accuracy. A wire can be obtained.

  According to the present invention, it is possible to provide a fixed abrasive wire that has good sharpness from the initial stage of cutting and has excellent processing efficiency and processing accuracy.

It is sectional drawing of the wire axial direction which shows a part of fixed abrasive wire which is embodiment of this invention. It is a partially expanded view of the fixed abrasive wire shown in FIG. It is a figure which shows the manufacturing process of the fixed abrasive wire shown in FIG. It is a table | surface which shows the cutting test conditions of the fixed abrasive wire shown in FIG. It is a graph which shows the outer diameter of the fixed abrasive wire before and behind a cutting test. It is a graph which shows the surface roughness of the silicon wafer after cut | disconnecting with a fixed abrasive wire. It is a graph which shows the thickness of the silicon wafer after cut | disconnecting with a fixed abrasive wire.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the fixed abrasive wire 10 of the present embodiment includes a metal wire 11 having flexibility and a part of a conductive coating layer 12 formed on a part of the surface. In order to fix the diamond abrasive grains 14 which are one of the superabrasive grains temporarily fixed by the first electrodeposition layer 13 in close contact with the outer peripheral surface of the wire 11 and the diamond abrasive grains 14 to the outer peripheral surface of the wire 11. A first electrodeposition layer 13 on the outer peripheral surface of the wire 11 and a second electrodeposition layer 15 that covers the coating layer 12 of the diamond abrasive grains 14. The coating layer 12 is made of Ni, and the first electrodeposition layer 13 and the second electrodeposition layer 15 are each formed by Ni plating.

  As shown in FIG. 2, in the fixed abrasive wire 10, the diamond abrasive grains 14 fixed to the outer peripheral surface of the wire 11 are in a state in which diamond is exposed at a tip portion 14 a that contacts a workpiece (not shown). Therefore, sharpness is good from the initial stage of cutting, and excellent machining efficiency and machining accuracy can be obtained. Moreover, since the diamond abrasive grain 14 with the tip portion 14a exposed directly bites into the workpiece during processing, the sharpness is good and the processing efficiency is improved. Further, since the diamond abrasive grains 14 are fixed by the first electrodeposition layer 13 and the second electrodeposition layer 15, the wire 11 is less bent during processing, and the thickness accuracy of the workpiece and the surface roughness of the cut surface are reduced. Etc., and the machining accuracy is remarkably improved.

  Further, as shown in FIG. 2, the surface 13a of the first electrodeposition layer 13 has an upper edge portion 12a of the coating layer 12 of the diamond abrasive grains 14 (the coating located at a portion away from the portion temporarily fixed to the wire 11). (Refers to the edge portion of the layer 12). The lower portion (region close to the outer peripheral surface of the wire 11) is in contact with the coating layer 12, and the boundary portion between the surface 13a of the first electrodeposition layer 13 and the coating layer 12 is A second electrodeposition layer 15 is formed so as to cover it.

  Further, in the boundary region X between the surface 15 a of the second electrodeposited layer 15 and the diamond abrasive grains 14, the surface 15 a of the second electrodeposited layer 15 faces the upper edge 12 a of the coating layer 12 of the diamond abrasive grains 14. The concave curved surface 15b has a smooth upward slope, and the upper edge portion of the concave curved surface 15b is integrated with the upper edge portion 12a of the coating layer 12 of the diamond abrasive grains 14. As a result, a state in which the second electrodeposition layer 15 is integrated with the first electrodeposition layer 13 at the upper edge portion 12a is formed, and it becomes difficult to receive an impact during processing, and abrasive grains fall off due to cracks and chips. Since it is difficult, the sharpness can be maintained.

  In addition, although the coating layer 12 of the diamond abrasive grain 14 is comprised with Ni, since it is not limited to this, it can also form with Cu, TiC, SiC, etc. Moreover, although the 1st electrodeposition layer 13 and the 2nd electrodeposition layer 15 are each formed with Ni, they can also be formed with Cu, Ni-P etc. other than this, for example.

  Further, if the coating layer 12 is formed on a specific crystal surface of the diamond abrasive grain 14, the crystal orientation of the diamond abrasive grain 14 can be aligned by adhering the coating layer 12 to the outer peripheral surface of the wire 11 and fixing it. Therefore, the wear rate of the diamond abrasive grains 14 can be made uniform, and the sharpness reduction rate caused by the wear of the diamond abrasive grains 14 can be reduced.

  On the other hand, in the present embodiment, by forming the coating layer 12 in the region of 50% of the surface area of the diamond abrasive grain 14, the diamond abrasive grain 14 is exposed to 50% of the surface area including the tip portion 14a. Since it is fixed to the outer peripheral surface of the wire 11 in a state, excellent processing efficiency and processing accuracy can be obtained. In addition, the coating layer 12 can be changed within the range of 20% to 80% of the surface area of the diamond abrasive grains 14.

  Furthermore, in this embodiment, when the thickness of the first electrodeposition layer 13 was set to 2 μm, the diamond abrasive grains 14 having the coating layer 12 and the wire 11 were well-fitted and a strong fixing force could be obtained. . When the thickness of the first electrodeposition layer 13 is out of the range of 1 μm to 10 μm, the adhesive force between the diamond abrasive grains 14 and the wire 11 becomes weak, and when it exceeds 10 μm, the flexibility of the wire 11 is increased. The above-mentioned range is desirable because it decreases, becomes weak against twisting, and easily breaks during use.

  Next, the manufacturing process of the fixed abrasive wire 10 will be described with reference to FIG. As shown in FIG. 3A, a conductive Ni coating layer 12 is formed on a part of the surface of the diamond abrasive grains 14. Since the formation method of the coating layer 12 is not limited, it can be formed by an electroplating method, a CVD method, a PVD method, an electroless plating method, or the like.

  On the other hand, as shown in FIG. 3B, a base nickel plating 16 is applied to the outer peripheral surface of the wire 11. The base nickel plating 16 is a pretreatment for the process of attaching the diamond abrasive grains 14 performed thereafter. In addition, before performing the base nickel plating 16, the degreasing process for cleaning the outer peripheral surface of the wire 11 and the hydrochloric acid process as the activation process for facilitating the adhesion of the base nickel plating 16 are performed in this order. Is performed on the outer peripheral surface of the wire 11.

  When the base nickel plating 16 is finished, as shown in FIG. 3C, the first electrodeposition layer is formed in a state in which a part of the coating layer 12 of the diamond abrasive grains 14 is in close contact with the surface of the base nickel plating 16 on the outer peripheral surface of the wire 11. 13 is temporarily fixed. In this case, since the coating layer 12 of the diamond abrasive grains 14 has conductivity, when the current flows only in the coating layer 12 in the Ni plating solution, the coating layer 12 adheres to the base nickel plating 16 surface, In this state, the diamond abrasive grains 14 are temporarily fixed by the first electrodeposition layer 13. The spacing adjustment of the plurality of diamond abrasive grains 14 is performed by changing the current and voltage in the plating process.

  When the temporary fixing of the diamond abrasive grains 14 to the outer peripheral surface of the wire 11 is finished, as shown in FIG. 3D, the first electrodeposition layer 13 and the coating layer 12 of the diamond abrasive grains 14 on the outer peripheral surface of the wire 11 are covered. By forming the second electrodeposition layer 15, the diamond abrasive grains 14 are fixed to the outer peripheral surface of the wire 11, and the fixed abrasive wire 10 is completed.

  Next, based on FIGS. 4-7, the difference in the cutting performance of the fixed abrasive wire 10 which concerns on this embodiment, and the conventional fixed abrasive wire is demonstrated. The fixed abrasive wire 10 according to the present embodiment (hereinafter referred to as “example”) has a diamond abrasive grain diameter of M12 / 25, an outer diameter of the wire 11 of φ120 μm, and an outer diameter of the fixed abrasive wire 10. Φ150 μm, the abrasive density is 100 to 150 particles / mm, and the tip end portion 14 a of each diamond abrasive grain 14 protrudes from the surface of the second electrodeposition layer 15 by about 6 μm to 23 μm.

  Moreover, the fixed abrasive wire (henceforth a "comparative example") described in Unexamined-Japanese-Patent No. 2006-181698 was used as a conventional fixed abrasive wire.

  When cutting experiments were performed on the fixed abrasive wires of Examples and Comparative Examples under the conditions shown in FIG. 4 and the outer diameters of the fixed abrasive wires before and after the experiment were measured, the results shown in FIG. 5 were obtained. Obtained. The outer diameter of the fixed abrasive wire before the cutting experiment is φ150 μm, but after the cutting experiment, the outer diameter of the example is φ148 μm, whereas the outer diameter of the comparative example is φ144 μm. When FIG. 5 is seen, it turns out that the direction of the fixed abrasive wire 10 of an Example is hard to wear compared with the fixed abrasive wire of a comparative example.

  Next, when the surface roughness Ra of the surface (cut surface) of the silicon wafer cut from the single crystal silicon subjected to the cutting experiment and the variation in the thickness of the silicon wafer are measured, the results shown in FIGS. 6 and 7 are obtained. was gotten. When FIG. 6 is seen, it turns out that the surface roughness when cut | disconnected with the fixed abrasive wire 10 of an Example is fine compared with a comparative example. Moreover, when FIG. 7 is seen, compared with a comparative example, it turns out that the variation in the thickness of the silicon wafer cut | disconnected with the fixed abrasive wire 10 of an Example is small.

  Moreover, it became clear that the fixed abrasive wire 10 of an Example has a favorable sharpness from the initial stage, and a processing precision and a tool life improve remarkably with respect to a comparative example. On the other hand, the fixed abrasive wire of the comparative example has poor initial stage sharpness and inferior processing accuracy, so in order to maintain the sharpness, it is necessary to use many fixed abrasive wires, Increased tool costs have occurred.

  The fixed abrasive wire of the present invention can be widely used in slicing of crystalline materials such as solar cells, semiconductor silicon, magnetic materials, sapphire, and SiC.

DESCRIPTION OF SYMBOLS 10 Fixed abrasive wire 11 Wire 12 Coating layer 12a Upper edge part 13 1st electrodeposition layer 13a, 15a Surface 14 Diamond abrasive grain 14a Tip part 15 2nd electrodeposition layer 15b Concave surface 16 Base nickel plating X Boundary area

Claims (5)

  A super-wire that is temporarily fixed by a first electrodeposition layer in a state in which a flexible wire having at least a surface conductivity and a part of a conductive coating layer formed on a part of the surface are in close contact with the outer peripheral surface of the wire Abrasive grains, and a second electrodeposition layer that covers the first electrodeposition layer on the outer peripheral surface of the wire and the coating layer of the superabrasive grains to fix the superabrasive grains to the outer peripheral surface of the wire. The fixed abrasive wire characterized by the above-mentioned.   The fixed abrasive wire according to claim 1, wherein the coating layer is formed on a specific crystal plane of the superabrasive grain.   The fixed abrasive wire according to claim 1 or 2, wherein the coating layer is formed in a region of 20% to 80% of the surface area of the superabrasive grains.   The thickness of the said coating layer is 2 micrometers-20 micrometers, The fixed abrasive wire in any one of Claims 1-3 characterized by the above-mentioned.   A step of forming a conductive coating layer on a part of the surface of the superabrasive grain; A step of temporarily adhering to the outer peripheral surface with a first electrodeposition layer; and a step of covering the electrodeposition layer on the outer peripheral surface of the wire and the coating layer of the superabrasive grains with a second electrodeposition layer. A fixed abrasive wire manufacturing method.

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