JP2006089586A - Magnetic abrasive grain and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic abrasive grain enabling precise surface processing and to provide a method for producing the abrasive grain. <P>SOLUTION: In the magnetic abrasive grain 1, an electroless plating layer 3 having magnetism is formed on diamond particles 2. The magnetic abrasive grain 1 can be produced by carrying out hydrophilization treatment of diamond particles 2 by using concentrated H<SB>2</SB>SO<SB>4</SB>/HNO<SB>3</SB>, adding a catalyst thereto and carrying out sensitizing treatment of the treated diamond particles and carrying out electroless plating and forming the electroless plating layer 3 having magnetism onto the surface of the diamond particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic abrasive grain and a manufacturing method thereof, and more particularly to a magnetic abrasive grain used for a magnetic polishing method and a manufacturing method thereof.

  The magnetic polishing method is a precision processing method for polishing the surface of a workpiece by moving abrasive grains having a polishing action by the action of a magnetic field. This magnetic polishing method is a method that enables polishing of parts that are difficult with conventional machining, such as the surface of a part having a complicated shape, the inner surface of a hole that does not receive a tool, the inner surface of a tube that does not reach the tool, etc. Part of the polishing has been put to practical use.

  Abrasive grains used in the magnetic polishing method move relative to the workpiece by the action of a magnetic field. In general, magnetic abrasive grains containing magnetic abrasive particles and magnetic abrasive grains made of a mixture of non-magnetic non-magnetic abrasive particles and magnetic particles are known. In the former case, the abrasive particles move by the magnetic field. In the latter case, the magnetic particles move by the magnetic field, and the abrasive particles move with the magnetic particles to polish the surface of the workpiece. To do. Therefore, the latter magnetic abrasive grains have a problem that the magnetic particles are easily worn and become polishing scraps, and the surface of the workpiece is contaminated.

On the other hand, the former magnetic abrasive grains do not have such a problem. For example, magnetic abrasive grains obtained by pulverizing a sintered body of magnetic particles and abrasive particles, or electroless plating film containing abrasive particles on the surface of the magnetic particles are formed. Magnetic abrasive grains (see, for example, Patent Document 1) have been reported.
JP 2002-265933 A (Claim 3)

  Although the magnetic abrasive grain described in Patent Document 1 described above is heavy and has a large polishing effect because most of its volume is occupied by magnetic particles having a high specific gravity, when performing a more precise polishing process, Since the surface of the workpiece was polished more than necessary, it was not necessarily a preferable abrasive grain.

  In recent years, high-precision surface polishing is required for super clean pipes and the like used for manufacturing processes in next-generation semiconductors and medical fields. However, the current magnetic abrasive grains have a problem that it is difficult to perform precision polishing on the surface of the workpiece, and the above requirements are still not fully satisfied.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetic abrasive grain capable of performing more precise surface polishing and a method for producing the same.

  In order to achieve the above object, the magnetic abrasive grains of the present invention are characterized in that an electroless plating layer having magnetism is formed on diamond particles.

  According to the present invention, since the electroless plating layer as the magnetic layer is formed on the diamond particle itself, which is an excellent abrasive particle, a high polishing ability that can be used in the magnetic polishing method is obtained. It becomes the magnetic abrasive grain which has. Since diamond is lighter than conventional magnetic abrasive grains having a large specific gravity, the magnetic abrasive grains can be easily moved during surface processing, so that workpieces having complicated shapes can be easily machined. There is.

  In the magnetic abrasive grains of the present invention, the diamond particles have an average particle diameter of 1 to 5 μm. According to the present invention, since the diamond particles themselves are used as the core of the magnetic abrasive grains, the size of the magnetic abrasive grains can be made extremely small, and more precise surface processing can be performed.

  In the magnetic abrasive grain of the present invention, the electroless plating layer is an electroless magnetite plating layer or an electroless nickel plating layer. In particular, an electroless magnetite plating layer having excellent magnetic properties is preferable. According to this invention, the magnetic abrasive grain applicable to a magnetic polishing method can be provided by forming the said plating layer.

  Further, in the magnetic abrasive grains of the present invention, the diamond particles are obtained by removing a part of the electroless plating layer formed on the diamond particles prior to or at the initial use of the magnetic abrasive grains. It is characterized in that a part of the surface is exposed. Since an electroless plating layer having magnetism is formed on the surface of the diamond particles, the surface of diamond functioning as abrasive grains is covered with the electroless plating layer immediately after its production. However, before or during the use of the magnetic abrasive grains of the present invention, the magnetic abrasive grains collide with each other or with other objects, so that the electroless plating layer is removed particularly at the convex portions on the diamond particle surface. As a result, the diamond surface that exhibits the polishing action is exposed. As a result, it can be effectively used as a magnetic abrasive having a high polishing action.

In order to achieve the above object, the method for producing magnetic abrasive grains of the present invention comprises hydrophilizing diamond particles using concentrated H ₂ SO ₄ / HNO ₃ , and then performing catalyst application / sensitization treatment, Electroless plating is performed to form a non-electrolytic plating layer having magnetism on the surface of diamond particles. In this manufacturing method, magnetic abrasive grains having excellent characteristics as described above can be manufactured by a relatively simple method.

  As described above, according to the magnetic abrasive grains of the present invention, magnetism can be imparted to diamond particles that are extremely hard and have excellent polishing performance, so that the magnetic abrasive grains are lightweight and have excellent polishing performance. Furthermore, precision polishing by a magnetic polishing method can be performed using the magnetic abrasive grains. For this reason, precision processing of the surface of a workpiece becomes possible, and a workpiece having a complicated shape can be easily processed. Further, since the diamond particles themselves are used as the core of the magnetic particles, there is no fear that the magnetic particles will be worn away by use, and stable characteristics can be exhibited for a long time.

  Hereinafter, the magnetic abrasive grains and the production method thereof according to the present invention will be described in detail with reference to the drawings.

(Magnetic abrasive)
FIG. 1 is a schematic cross-sectional view showing an example of the magnetic abrasive grains of the present invention. The magnetic abrasive grain 1 of the present invention has a configuration in which an electroless plating layer 3 having magnetism is formed on the surface of diamond particles 2. In FIG. 1, the surface of the diamond particle 2 is coated with the electrolytic plating layer 3, but the magnetic abrasive according to the present invention is formed on the diamond particle 2 before or at the beginning of use. By removing a part of the electroplating layer 3, a part of the projections on the surface of the diamond particles 2 serving as the core is exposed.

  The diamond particle 2 is a base that forms the core of the magnetic abrasive grain 1, and any of artificial and natural ones can be used. The particle size of the diamond particles 2 can be appropriately selected according to the material and shape of the workpiece to be processed and the purpose of processing the workpiece, but those having a large particle size are generally expensive. In addition, it is desirable that the particle size is small to some extent from the viewpoint of ultraprecision machining. From such a viewpoint, the average particle diameter of the diamond particles 2 is usually 1 to 5 μm, and more preferably 1 to 3 μm.

The electroless plating layer 3 formed on the surface of the diamond particles 2 only needs to have a magnetic property capable of moving the diamond particles by at least a magnetic field. The material for forming the electroless plating layer 3 is preferably an iron-based magnetic material such as magnetite (Fe ₃ O ₄ ), or a magnetic material made of nickel or a nickel alloy. As a nickel alloy, a Ni-P alloy and a Ni-B alloy can be mentioned preferably, and other elements may be contained in these alloys.

Magnetite (Fe ₃ O ₄ ) is particularly desirable because it exhibits high magnetism. Further, it is desirable that the magnetite (Fe ₃ O ₄ ) is attached as particles rather than the case where the magnetite (Fe ₃ O ₄ ) is attached as a layer on the surface of the diamond particles 2. Magnetite (Fe ₃ O ₄ ) adhering to the surface of the diamond particle as a particle reliably adheres to the diamond particle and exhibits high characteristics as a magnetic substance.

The thickness of the electroless plating layer 3 may be any thickness that can ensure the magnetic characteristics required for the magnetic abrasive grains 1 for magnetic polishing. Therefore, the thickness of the material for forming the electroless plating layer 3 is not limited. It is desirable to change appropriately according to the type. In the present invention, preferred examples of the material for forming the electroless plating layer 3 include magnetite (Fe ₃ O ₄ ), Ni—P alloy, Ni—B alloy and the like, and the electroless plating layer 3 made of these materials. Is preferably formed on the above-described 1 to 5 μm diamond particle 2 with a thickness of about 10 to 100 nm. More preferably, the electroless plating layer 3 is partially formed on the diamond particles, but even when it is not partially formed, as described above, prior to its use or in the initial stage of use, By removing a part of the electroless plating layer 3 formed on the diamond particles 2, it is only necessary to partially expose the convex portions on the surface of the diamond particles 2 serving as nuclei. As will be described later, when the magnetic abrasive grains 1 are used as the constituent material of the magnetic abrasive liquid, the thickness of the electroless plating layer 3 is adjusted in consideration of the specific gravity of the liquid medium constituting the magnetic abrasive liquid.

(Method for producing magnetic abrasive grains)
As a method for producing magnetic abrasive grains of the present invention, a method for forming an electroless plating layer on the surface of diamond particles by electroless plating will be described in detail.

In the method for producing magnetic abrasive grains according to the present invention, first, diamond particles are hydrophilized using concentrated H ₂ SO ₄ / HNO ₃ . Since the surface of the diamond particles is hydrophobic as is well known, the plating solution does not get wet (cannot contact) on the surface of the diamond particles when immersed in an electroless plating solution as it is, and a plating layer is difficult to form. For this reason, in this invention, the hydrophilic treatment of the diamond particle 2 is performed as a pretreatment of plating.

The hydrophilic treatment liquid is preferably concentrated H ₂ SO ₄ / HNO ₃ liquid, and the mixing ratio is preferably about 9: 1 by volume ratio. Then, by immersing the diamond particles in a concentrated H ₂ SO ₄ / HNO ₃ liquid kept at about 90 ° C. for about 30 minutes, the surface of the diamond particles can be hydrophilized.

  After the hydrophilization treatment, the hydrophilization solution and the diamond particles are separated by filtration, centrifugation, or the like, and then the separated diamond particles are sufficiently washed with water or the like.

  Next, a catalyst is applied to the surface of the hydrophilized diamond particles, and further sensitization is performed. This catalyst application / sensitization treatment is the same as the catalyst application / sensitization treatment that is generally performed to facilitate plating when electroless plating is performed on a non-metallic surface such as glass or plastic. For example, the catalyst imparting / sensitization treatment is performed by adsorbing a metal element or metal complex on the surface of diamond particles using a tin solution, a palladium solution or a tin-palladium complex solution, and further adsorbing the adsorbed metal element or metal complex. This is a treatment for generating an active metal element on the surface by oxidation-reduction reaction or the like.

  The diamond particles subjected to the catalyst application / sensitization treatment in this way are immersed in an electroless plating solution containing ionic species that will have magnetic properties after film formation. An electroless plating layer having magnetic properties can be generated by immersing the diamond particles subjected to the catalyst application / sensitization treatment in a plating solution. The principle of such electroless plating is that the reducing agent in the plating solution is oxidized by the catalytically active metal element (for example, palladium) adhering to the surface of the diamond particle, and the magnetic substance in the plating solution is formed by the electrons released at that time. As a result, an electroless plating layer having magnetic properties is generated.

  In the electroless plating treatment, it is preferable to uniformly disperse the diamond particles in the plating solution so that an electroless plating layer having a predetermined thickness can be formed on the surface of each diamond particle 2. It is preferable to use stirring means such as mechanical stirring, gas stirring such as air, and ultrasonic stirring using an ultrasonic homogenizer.

(Magnetic abrasive fluid)
The magnetic abrasive according to the present invention can be used as it is, for example, as an abrasive for precision machining such as a magnetic polishing method, or as a magnetic abrasive liquid together with a liquid medium.

  When the magnetic abrasive grains of the present invention are used as the constituent material of the magnetic abrasive liquid, the thickness of the electroless plating layer 3 is changed to adjust the weight of the magnetic abrasive grains, and the degree of floating in the magnetic abrasive liquid It is also possible to adjust the degree of sedimentation.

  The liquid medium constituting the magnetic abrasive liquid may be any medium that allows the magnetic abrasive grains to freely move, and is appropriately selected in consideration of the type of workpiece and the specific gravity of the magnetic abrasive grains. For example, water, water-based lubricant, oil, oil-based lubricant, etc. can be used. Further, the content of the magnetic abrasive grains in the magnetic abrasive liquid is also appropriately adjusted according to the processing application and the workpiece.

(Use of magnetic abrasive grains)
The magnetic abrasive grains of the present invention can be expected to be applied to precision processing of various workpieces by the magnetic polishing method. For example, precision abrasive pipes used in next-generation semiconductors and manufacturing processes in the medical field, etc. It is effective for polishing products that require polishing and products that require high-precision polishing of a minute space such as in a pipe. In addition, for example, application to texture processing of a hard disk substrate surface of a hard disk device can be mentioned. Further, for example, application as an alternative process of chemical mechanical polishing (CMP) used in a damascene process for forming a copper wiring on a semiconductor substrate can be expected. The damascene process is a process of removing unnecessary copper on the surface after forming a barrier layer and a copper plating layer in a wiring groove on an insulating film. The magnetic abrasive grains of the present invention are not limited to such applications, and can be widely applied to various uses that can exhibit the functions of the magnetic abrasive grains of the present invention.

  FIG. 2 is an example of a magnetic polishing apparatus for carrying out the magnetic polishing method of the present invention. The magnetic abrasive grains of the present invention are not limited to application to such a magnetic polishing apparatus.

  The magnetic polishing apparatus of FIG. 2 is mainly composed of a tube support portion (not shown) that rotatably supports a circular tube 71 that is a workpiece, and a magnetic pole 72 that is disposed outside the circular tube 71. It is configured.

  For example, four magnetic poles 72 are arranged in the circumferential direction at approximately 90 ° intervals via yokes 73. The yoke 73 on which the magnetic pole 72 is disposed is provided so as to be capable of reciprocating (for example, amplitude) in the axial direction of the circular tube 71. As the yoke 73 reciprocates in the axial direction of the circular tube 71, the magnetic pole 72 swings in the axial direction of the circular tube 71. The magnetic pole 72 applies a magnetic field to the circular tube 71, and a permanent magnet or an electromagnet is used. Also, the number and arrangement of the magnetic poles 72 are arbitrarily set. The magnetic abrasive grains 70 put in the circular tube 71 are attracted to the inner wall of the circular tube 71 by a magnetic field applied in the circular tube 71. This force becomes a processing force in magnetic polishing, and magnetic abrasive grains press the inner wall of the circular tube 71 to generate a pressing force.

  When the circular tube 71 is rotated in the circumferential direction in this state, the magnetic abrasive grains 70 move relative to the inner surface of the circular tube 71, and the inner surface of the circular tube is polished. Although the case where the circular pipe 71 is rotated to perform the polishing process has been described, the circular pipe 71 may be fixed and the magnetic pole 72 may be rotated to perform the polishing process, or both the circular pipe 71 and the magnetic pole 72 may be connected. Polishing may be performed by rotating.

  The magnetic polishing method of the present invention is not limited to the case of polishing the inner surface of a circular tube, and can be widely applied to the various uses described above that can exhibit the function of the magnetic abrasive grains of the present invention. As an example, as described above, application to polishing processing of the inner surface of a super clean pipe used for next-generation semiconductors and manufacturing processes in the medical field, and texture processing of a hard disk substrate surface of a hard disk device can be expected. Moreover, application as an alternative process of chemical mechanical polishing (CMP) used in a damascene process for forming a copper wiring on a semiconductor substrate can be expected.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
Diamond particles having an average particle diameter of 2.1 μm (Tomei Diamond Co., Ltd.) were used as diamond particles. First, in order to hydrophilize the surface of the diamond particles, the diamond particles are immersed in concentrated H ₂ SO ₄ / HNO ₃ (mixing volume ratio 9: 1) kept at about 90 ° C. for 30 minutes, and then diamond The particles were removed by filtration and washed thoroughly with water.

  Next, the hydrophilized diamond particles were immersed in (i) tin solution (product name: S-10X, manufactured by Uemura Kogyo Co., Ltd.) for 1 minute, (ii) washed with water for 1 minute, and (iii) palladium solution (Uemura Industries). (I) (product name: A-10X) for 1 minute, (iv) 1 minute washing with water is repeated twice (i) to (iv), and the surface of the hydrophilized diamond particles is imparted with catalyst and increased. Sensation was processed.

The electroless plating _{solution, Fe (NO 3) 3 ·} 9H 2 O: 0.1mol / L, dimethylamine borane (liter same..): 0.03mol / L, glycine: 0.5 mol / L, nitrate Lead: An electroless magnetite (Fe ₃ O ₄ ) plating solution containing 1 mg / dm ³ and adjusted to pH 9.0 with ammonia was prepared. To this electroless magnetite plating solution, 1.6 g / L of the diamond particles subjected to the above hydrophilization treatment and catalyst application / sensitization treatment are added, plating solution temperature: 50 ° C. ± 1 ° C., plating time: 30 minutes, nitrogen Electroless magnetite plating was performed to a thickness of about 1 μm under stirring conditions, and the magnetic abrasive grains of Example 1 were obtained.

FIG. 3 is a scanning electron micrograph (25,000 times magnification) showing the surface state of diamond particles before plating treatment, and FIG. 4 is a scanning electron micrograph showing the surface state of diamond particles after Fe ₃ O ₄ plating treatment ( FIG. 5 is a scanning electron micrograph (magnification 40,000 times) in which the surface of the diamond particles after the Fe ₃ O ₄ plating treatment is further enlarged. As shown in FIGS. 4 and 5, it can be seen that magnetite (Fe ₃ O ₄ ) particles are deposited on the surface of the diamond particles by electroless plating to form a plating layer having a thickness of about 1 μm. From the results of scanning electron micrographs, Fe ₃ O ₄ is not formed as a uniform layer like a general plating layer, but magnetite particles deposited on the surface of diamond particles are stacked to form a layer. I found out. The magnetic abrasive grains having such an aspect are strong in magnetism because magnetite (Fe ₃ O ₄ ) particles are deposited on the surface of the diamond particles and formed into a layer. FIG. 6 shows the results of analyzing the obtained magnetic abrasive grains using an X-ray diffractometer (XRD).

(Example 2)
The magnetic abrasive of Example 2 is the same as Example 1 except that the plating layer formed on the surface of the diamond particles is an electroless Ni-B plating layer, and the diamond particles, hydrophilization treatment, and catalyst application / sensitization treatment are the same as in Example 1 above. Grains were made.

The electroless Ni-B plating solution is nickel sulfate: 0.1 mol / L (liter, the same applies hereinafter), dimethylamine borane: 0.025 mol / L, glycine: 0.5 mol / L, lead nitrate: 1 mg / dm ³ An electroless Ni-B plating solution adjusted to pH 9.0 with ammonia was prepared. To this electroless Ni-B plating solution, 1.6 g / L of the diamond particles subjected to the above hydrophilization treatment and catalyst application / sensitization treatment are added, plating solution temperature: 70 ° C. ± 1 ° C., plating time: 7 minutes. Then, electroless Ni-B plating was performed so as to have a thickness of about 1 μm under air stirring conditions, and magnetic abrasive grains of Example 2 were obtained.

It is a schematic cross section which shows an example of the magnetic abrasive grain of this invention. It is a schematic perspective view which shows an example of a magnetic polishing apparatus. 2 is a scanning electron micrograph (magnification 25,000 times) of diamond particles used in Example 1 and Example 2. FIG. 2 is a scanning electron micrograph (magnification 25,000 times) of the magnetic abrasive grains of Example 1. FIG. 2 is a scanning electron micrograph (magnification 40,000 times) obtained by further enlarging the magnetic abrasive grains of Example 1. 2 is an XRD chart of magnetic abrasive grains of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic abrasive grain 2 Diamond particle 3 Electroless plating layer

Claims (6)

  A magnetic abrasive comprising a nonelectrolytic plating layer having magnetism formed on diamond particles.   3. The magnetic abrasive according to claim 1, wherein the diamond particles have an average particle diameter of 1 to 5 μm.   The magnetic abrasive according to claim 1 or 2, wherein the electroless plating layer has a thickness of 10 to 100 nm.   The magnetic abrasive grain according to any one of claims 1 to 3, wherein the electroless plating layer is an electroless magnetite plating layer or an electroless nickel plating layer.   Prior to the use of the magnetic abrasive grains or in the initial stage of use, the diamond particles are such that a portion of the electroless plating layer formed on the diamond particles is removed and a part of the surface of the diamond particles is exposed. The magnetic abrasive grain according to any one of claims 1 to 4, wherein: The diamond particles are hydrophilized using concentrated H ₂ SO ₄ / HNO ₃ , then subjected to catalyst application and sensitization, and then subjected to electroless plating, whereby the surface of the diamond particles is magnetized. The manufacturing method of the magnetic abrasive grain characterized by forming a plating layer.

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