JP2008221406A - Fixed abrasive grain type wire saw and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the cost of a wire saw by using stainless steel as a wire material by improving the joining structure of diamond and a wire in a fixed abrasive grain type wire saw. <P>SOLUTION: In this wire saw, a first layer 6 of coating diamond 5 in which multi-layer coating 4 is performed on an outer periphery of the wire 1 via a brazing material 2 contains transition metal such as Ti and is a layer chemically bonded to a diamond material 3. A second layer 7 is made of a wettability improvement layer against the brazing material 2. A third layer 8 for the wettability improvement layer against the brazing material 2 is provided according to circumstances. The wire 1 is made of a stainless steel material causing no substantially lowering of strength when performing heat treatment when the coating diamond 5 is fixed by the brazing material 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixed-abrasive wire saw used in a slicing process of various electronic materials typified by a single crystal of silicon and a manufacturing method thereof.

  The fixed abrasive wire saw used in the slicing process of various electronic materials is obtained by fixing superabrasive grains (hereinafter collectively referred to as “diamond”) such as diamond and CBN on the outer periphery of the wire. There are a resin bond method and an electrodeposition method as diamond fixing methods. Each of these methods has major flaws. In order to improve this, a diamond fixing method by brazing, a so-called chemical bond method is known (see Patent Document 1).

The one disclosed in Patent Document 1 is obtained by fixing diamond to a wire with an active brazing material having a thickness of 5 to 35% of the particle diameter of the diamond. As the active brazing material, a Cu-Ag-Ti alloy is used. As the wire, a tungsten wire that can withstand the melting temperature (850 to 1050 ° C.) of the active brazing material is used. Tungsten wire is an optimal material because its strength deterioration is 20% or less even at high temperature treatment at 1400 ° C.

The active brazing material has a characteristic that the active element Ti reacts with the diamond element C to form a carbide (TiC), thereby being chemically bonded. A fixed-abrasive wire saw manufactured by such a chemical bond method is characterized by high diamond retention, excellent cutting performance, and high productivity.
JP 2006-123024 A

  In the above-mentioned fixed abrasive type wire saw, it is necessary to select a material having a strength deterioration of 20% or less at the melting temperature (850 to 1050 ° C.) of the active brazing material as the wire material. Wire is used. However, the price of tungsten is rising with the increase in consumption in recent years, and it is expected that the price will increase further in the future, and the active raw material is also expensive. There is a problem of high cost. In order to spread the use of fixed-abrasive wire saws, it is desired to develop inexpensive wire saws.

  Therefore, the present invention improves the fixing means of the wire and diamond, and has the same characteristics as those of the conventional example described above in terms of diamond holding power, cutting performance, productivity, etc., but is inexpensive as a wire and brazing material. It is an object of the present invention to provide a fixed-abrasive wire saw and a method for manufacturing the same, which can reduce the cost by allowing the product to be used.

  In the invention relating to the fixed abrasive wire saw for solving the above problems, as shown in FIGS. 1A and 1B, the coating diamond 5 is fixed to the outer periphery of the wire 1 via the brazing material 2. It is a thing. This coating diamond 5 is obtained by forming a multilayer coating layer 4 on the surface of the diamond material 3, and the first layer 6 of the multilayer coating layer 4 is a layer containing a transition metal such as Ti having strong adhesion activity with diamond. In addition, strong bonding is achieved by chemical bonding at the interface with diamond. The second layer 7 is a wettability improving layer for the brazing material 2. For example, the coating of the second layer by electroless plating of Ni-P has good workability and greatly improves the poor wettability (bondability) to the brazing material of the first layer. By performing the heat treatment, the bonding strength between the first and second layers is increased, so that it is suitable as a wettability improving layer. The wire 1 is made of a steel material having a substantial strength decrease of 20% or less during brazing in which the coating diamond 5 is fixed by the brazing material 2. In general, steel materials include high-speed steel and die steel that have a low decrease in strength (hardness) at high temperatures. However, they are hard and do not have toughness, so it is difficult to draw them into wire materials.

  Various stainless steels can be easily drawn with a die, and the strength is increased by work hardening, and it can be said that stainless steel is most suitable as a wire saw material. Precipitation hardening type stainless steels such as SUS301, 304 and SUS630, 631 can be said to be suitable materials.

  The relationship between temperature increase and hardness decrease is a combination of temperature and time. That is, the decrease in hardness can be extremely small even at 600 ° C. or higher for a short time, and it can be cured and increased in strength at an appropriate temperature.

  As a result of the experiment, for example, with Φ0.18 mm stainless steel SUS631 that has been well drawn and cold worked, the hardness of the material is Hv551, and when this is heat treated at 600 ° C. for 30 seconds, the hardness is Hv743 To rise. Similarly, with SUS304, the hardness of the material was Hv603, and it was found that Hv increased to 722 when treated at 600 ° C for 30 seconds. If the temperature at which diamond is brazed to the wire is set to 600 ° C for 30 seconds, the wire material will not be softened by brazing, and the effect of two birds with one stone can be expected.

  When the brazing temperature is 650 ° C., the decrease in wire hardness can be suppressed within 20% by shortening the treatment time to about 10 seconds.

  The brazing material is generally a Cu-Ag-based material called so-called silver brazing, but many of the easily available brazing materials melt at 650 to 750 ° C. For example, when SUS steel is used as the wire material, the temperature can be reduced to 20% or less with a temperature treatment of about 700 ° C for a short time, but as a wire saw, the hardness is as high as possible (high tensile strength) ) Is more desirable. From this point of view, it is desirable to select a brazing material within a range in which the hardness of the wire material does not decrease, and it is best to braze under the condition that the hardness by precipitation hardening becomes high. That is, it is possible not only to soften the wire in consideration of the material of the wire saw material, the brazing temperature, and the processing time, but also to strengthen the wire. When using a stainless steel wire such as SUS631 or SUS304, the brazing temperature is preferably in the vicinity of 600 to 650 ° C, and of course, if the time is shortened, it is possible to exceed 650 ° C. In consideration of the above, it is necessary to select a brazing material having a temperature capable of stably brazing in the range of 500 to 650 ° C.

However, the brazing temperature of the brazing material can be adjusted by adding a low melting point metal such as Sn or In based on a commercially available brazing material having a low melting temperature. Research on brazing materials that can be brazed at low temperatures is also progressing in various places, and it is easy to obtain or prepare. (According to Japanese Patent Laid-Open No. 8-57682, by adding In and Sn to Ag, a brazing material having a melting temperature of 500 to 600 ° C. can be made.)
That is, a metal coating containing Ti or the like that can be firmly bonded to diamond on the surface of the diamond (actually, when the coating layer is thin, it is almost chemically bonded to diamond to form a TiC film). A metal coating such as Ni-P is applied, and this is heat treated to enhance the bonding strength at the interface between the Ni-P layer and TiC. Then, the diamond surface is covered with metal. In this state, the metal wire and the metal-coated diamond can be fixed to the wire with a general brazing material without using an active brazing material having a high melting temperature. Ni-based metal makes it easy to form a thin and strong oxide film, and it is difficult to adjust the atmosphere when brazing. To make brazing easier, copper (Cu) is further added outside the Ni-based metal coating film. Coating makes it easier to braze and broadens the range of choice of brazing material. An appropriate diamond wire saw can be realized by appropriately selecting a combination of temperature and time for the brazing material so that the wire material softens and the strength does not drop below 20%.

  According to the present invention, the process involving high-temperature heat treatment for coating the diamond material 3 with a transition metal such as Ti having strong adhesion activity and forming an adhesion activation layer by chemical bonding with the diamond material 3 comprises coating diamond 5 Therefore, it is possible to avoid the thermal influence on the wire 1 during the high-temperature heat treatment.

  Moreover, the brazing material used in the brazing step can be prepared by using a normal brazing material, or by adding a small amount of cheap metal, it is possible to prepare a brazing material that melts in the vicinity of 600 ° C. As a material of the wire 1, an inexpensive steel material such as stainless steel can be used as a material having heat resistance matched to the brazing material. As a result, the cost of the brazing material and the wire can be reduced, and at the same time it has the same characteristics as those for fixing the diamond with the active brazing material to the tungsten wire in terms of diamond holding power, cutting performance, productivity, etc. An inexpensive fixed-abrasive wire saw can be provided.

  Examples of the present invention will be described below.

  The fixed abrasive wire saw of Example 1 is based on the configuration described above based on FIGS. 1 (a) and 1 (b). That is, innumerable coating diamonds 5 are fixed to the outer periphery of the wire 1 via the brazing material 2.

  The coating diamond 5 is obtained by forming a multilayer coating layer 4 on the surface of diamond. The first layer 6 of the multilayer coating layer 4 is a layer strongly bonded to diamond containing a transition metal such as Ti by chemical bonding, and the second layer 7 is a wettability improving layer for the brazing material 2.

  Examples of the metal forming the first layer 6 include Ti, Cr, V, Mn, Nb, W, Mo, Fe, Co, Ni, Pd, Pt, Rh, Ta, Re, Hf, Zr, U, and Ce. There are transition metals. Among them, Ti has the strongest adhesion activity and has established a coating technique for diamond, and can be said to be the most preferable element. The treatment temperature when the first layer is coated on the diamond material 3 with Ti is, for example, as high as 800 ° C. or higher according to the molten salt method. Chemical bonding is performed and the diamond material 3 is firmly bonded.

  A coating film in which Ti, TiC film is coated on the diamond surface at a low temperature, such as sputtering, and then heat-treated at a high temperature to enhance the bonding force between the Ti-based film and diamond is also within the scope of the present invention. Shall be included.

  Since the TiC film does not get wet with a general brazing material that melts at 700 ° C. or lower, it cannot be brazed onto a metal wire.

  As a countermeasure, a wettability improving layer is coated as the second layer 7 on the TiC film. In this case, the wettability improving layer is coated with a Ni-based alloy such as Ni-P or Ni-B by electroless plating. In addition to electroless plating, Ni-based alloy coating can be performed by sputtering or the like, but electroless plating with good workability and a proven coating method is optimal.

Since the Ni-based alloy film such as Ni-P coated by electroless plating is only attached to the TiC film surface, a strong bonding force cannot be obtained between the layers. In order to reinforce the interlayer bonding force, heat treatment was performed at 850 ° C. in an Ar or H ₂ gas atmosphere for 15 minutes. In order to confirm the improvement in bonding strength by the heat treatment, the following comparative experiment was conducted.

"Comparison experiment"
The coating diamond 5 was subjected to the above heat treatment, and this and the brazing material were mixed at the same ratio (volume ratio), and a lump obtained by vacuum hot pressing at 750 ° C. was produced. Breaking the lump and observing the fracture surface with a microscope, the fracture is almost in diamond grains, diamond- (TiC), (TiC)-(Ni-P), (Ni-P) -raw and brazing. It occurred evenly. From this result, it can be said that there is no interlayer with particularly weak bonding.

  As a comparison object, the same coated diamond 5 not subjected to the above heat treatment was made into a lump under the same conditions as described above, and when this was broken, the fracture surface was observed under a microscope. As a result, about 90% was (TiC)-(Ni-P ).

  This is because there is no particularly weak spot even when a strong force to break the coating diamond 5 is applied by the heat treatment at 850 ° C. for 15 minutes, and the bonding strength between (TiC)-(Ni-P) is low. It proves that it was strengthened by the heat treatment.

In addition, heat treatment at 900 ° C. or higher is possible, and this can further improve the above-mentioned bonding force, but as a result of melting Ni—P, there is a disadvantage that the coating diamond 5 is bonded to each other. ("Comparison experiment" and above)
The coating diamond 5 as described above is manufactured in advance, and this is brazed to the wire 1. FIG. 2 is a schematic view of the brazing apparatus, in which a wire bobbin 11 is installed at the lower stage, a brazing material crucible 12, a diamond crucible 13 and a winding bobbin 14 are arranged at the uppermost stage in that order from the bottom. The bottom of each crucible 12, 13 is formed in a funnel shape, and heaters 15, 16 are provided on the outer peripheral surface of the cylindrical portion of the lower brazing crucible 12 and the outer peripheral surface of the conical portion of the upper diamond crucible 13, respectively. The wire 1 wound around the wire bobbin 11 is penetrated through the pores at the upper and lower ends of the crucibles 12 and 13 and wound around the winding bobbin 14.

  When the winding system is driven, the wire 1 passes through the brazing crucible 12 in a heated and melted state, so that the brazing material 2 having a predetermined thickness is attached to the wire 1 and then passes through the diamond crucible 13. Through the brazing material 2, the coating diamond 5 is attached with a density adjusted appropriately. The heater 16 of the crucible 13 is provided to prevent the brazing material 2 from being cooled. The wire 1 that has passed through the diamond crucible 13 is naturally cooled, and the coating diamond 5 is firmly fixed to the wire 1.

  As the brazing material 2, an ordinary brazing material that melts around 650 ° C. can be used as it is easy to adhere to the second layer of the coating diamond 5. A Cu alloy-based (for example, Cu—Ag—Zn—Sn) brazing material is one of the preferred brazing materials because it is inexpensive and has high adhesive strength. More preferably, when a brazing material is prepared and used so that the melting temperature is 600 ° C., the wire is less softened, but rather the hardness is increased by precipitation hardening as described above, and the wire 1 is strengthened.

  Since the wire 1 only receives heat only in the brazing step, a material that can substantially suppress a decrease in strength to 20% or less when exposed to heat for a short time during heat treatment at 650 ° C. or less, for example, Stainless steel can be used.

  In addition, while setting the thickness of the brazing material 2 to 5 to 35% of the coating diamond particle size, a part of the coating diamond 5 is buried in the brazing material 2 and fixed to the wire 1, Since most of the remaining portion is exposed from the brazing material 2, the cutting fluid is circulated smoothly and chips are discharged smoothly, and high cutting performance is exhibited.

  In the coated diamond 5 of Example 1, when the high-temperature heat treatment was performed in the above-described reducing atmosphere in order to enhance the bonding force between the first layer 6 and the second layer 7, the Ni-P of the second layer The oxide film on the surface is reduced, but a thin oxide film can be formed by reheating around 600 ° C during brazing. For this reason, since the atmosphere when brazing the wire 1 and the purity of the gas are affected, there is a concern that it is costly to control various conditions in order to fix the coating diamond 5 stably.

  As a countermeasure, in the case of Example 2, it is more desirable to coat Cu by electroless plating as the third layer 8 as shown in FIG. Before the Cu coating, the diamond surface coated with Ni-P is acid-treated, and after removing the oxide film and activating the surface and plating with Cu, a coating with good adhesion can be obtained. As a result, the surface of the coating diamond 5 is covered with Cu. Cu oxide film is easier to reduce than Ni oxide film than Ni oxide film, easier to braze to Cu surface than steel materials, and better wetting of brazing material, stable and less susceptible to atmosphere And can be brazed. The method of brazing the coated diamond 5 of Example 2 having the three layers 6, 7, and 8 as described above to the wire 1 is the same as that of Example 1.

  In order to confirm the bonding state at the interface between the Cu of the third layer 8 and the Ni-based alloy (Ni-P) of the second layer, the following experiment was performed.

"Experimental example"
A Cu coating layer formed by electroless plating as the third layer 8 on the second layer 7 of the coated diamond 5 of Example 1 was subjected to heat treatment in an Ar or H ₂ stream at 400 ° C. to form Cu. The oxide film on the surface is removed. Further, it was found that Cu and Ni—P diffuse and completely alloy by heat treatment in a reducing atmosphere at 500 ° C. for 15 minutes. (More than experimental example)
From the above experiment, since the heat treatment for increasing the bonding strength between the second layer and the third layer can be performed at a temperature around 600 ° C. at the time of brazing, the bonding strength at the interface between the second layer and the third layer. A special heat treatment step for strengthening is unnecessary, and the heat of fusion is conducted to the interface during brazing, so that alloying is performed by diffusion of the second layer (Cu) and the third layer (Ni-P). Is called. That is, at the same time as brazing, the bonding strength enhancing process at the interface between the second layer and the third layer is performed.

  When the coating diamond 5 is finally covered with Cu, Cu brazing becomes easy. For example, it is the cheapest copper-phosphorus brazing material, Cu does not require flux and can be easily brazed with a gas burner. Thus, the brazing stability can be achieved by coating the outermost layer of the diamond coating 5 with Cu having better brazing properties.

(A) is a partially enlarged cross-sectional view of Example 1 or 2, (b) is a partially enlarged cross-sectional view of (a) in the case of Example 1, and (c) is (a) in the case of Example 2. Partial enlarged sectional view of the figure Schematic of the manufacturing apparatus of Example 1 or 2

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wire 2 Raw material 3 Diamond material 4 Multi-layer coating layer 5 Coating diamond 6 1st layer 7 2nd layer 8 3rd layer

Claims (7)

  In a fixed-abrasive wire saw in which diamond is fixed to the outer periphery of the wire via a brazing material, the diamond is a coated diamond having a multi-layer coating on the entire surface, and the first layer is a transition metal such as Ti A layer that is bonded by chemical bonding at the interface with the diamond, the second layer is made of a wettability improving layer with respect to the brazing material, and the brazing heat treatment when the wire is fixed to the coating diamond by the brazing material A fixed-abrasive wire saw characterized in that it is made of a steel material whose substantial strength drop is 20% or less.   The first layer is a TiC film formed by reacting with C of diamond by coating Ti, and the second layer is a Ni-based alloy coating layer. Fixed abrasive wire saw.   3. The coating layer according to claim 1, wherein a coating layer is formed on the second layer as the third layer, which has excellent brazing properties such as a copper coating and can be firmly bonded to the second layer. Fixed abrasive wire saw.   The fixed abrasive wire saw according to any one of claims 1 to 3, wherein the brazing material is a brazing material that melts at a temperature at which the strength reduction of the wire material is substantially within 20% or less.   The fixed steel abrasive wire saw according to any one of claims 1 to 4, wherein the steel material is stainless steel.   In the manufacturing method of the fixed abrasive type wire saw in which diamond is fixed to the outer periphery of the wire via the brazing material, the outer surface of the diamond is coated with a transition metal such as Ti as the first layer, and the second layer is applied to the brazing material. After coating the wettability improving layer, a high-temperature heat treatment is performed to pre-manufacture a coating diamond whose first layer and the second layer are bonded to each other, and the coating diamond is brazed to the wire. A method for manufacturing a fixed-abrasive wire saw.   When the coating diamond is pre-manufactured, after the high-temperature heat treatment, the third layer forms a coating layer that has excellent brazing properties such as copper coating and can be firmly bonded to the second layer. The manufacturing method of the fixed-abrasive wire saw according to claim 6.

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