JP2007326183A - Magnetic polishing liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adopt a composition containing water as a solvent in order to make it advantageous in terms of environmental safety, and furthermore, there is no interference with other compositions, high stability of dispersion state, and good polishing ability can be obtained. A magnetic polishing liquid is provided.
A magnetic polishing liquid includes at least four components of magnetic particles 41, polishing particles 42, resin particles 43, and a solvent 44. The solvent 44 is water, and the resin particles 43 are resin materials that do not dissolve in the solvent. And a composition in which a polyhydric alcohol such as glycerin is added as an additive for improving drying control and dispersion stability. When the magnetic field of the permanent magnet 20 acts, the magnetic particles 41 are attracted to each other and magnetic clusters are generated. Since the resin particles 43 are present between the magnetic particles 41, the resin particles 41 become elastic members that are elastically deformed in the flow operation during polishing, and also function as spacer members that increase the bulk of the magnetic clusters.
[Selection] Figure 2

Description

  The present invention relates to a magnetic polishing liquid for performing non-contact fluid polishing by interlocking with the action of a magnetic field, and more specifically, at least magnetic particles, polishing particles, resin particles, and a solvent. The present invention relates to an improvement regarding a composition containing four components.

  As polishing techniques for precisely polishing the surface to be polished, processing methods such as lapping, CMP (Chemical Mechanical Polishing), and float polishing are well known.

  Further, as a final polishing using magnetism, a polishing technique using a magnetic fluid (MF) or a magnetorheological fluid (MRF) is known, and MF or MRF is mixed with abrasive grains. Polishing is performed by moving the liquid mixture by a magnetic field.

  However, such conventional magnetic polishing techniques have the following problems. Magnetic polishing by MF requires a long time magnetic polishing because magnetic particles are weakly fixed when a magnetic field is applied and polishing efficiency is low. Further, since MF is obtained by uniformly dispersing magnetic particles having a particle diameter of about 10 nm, it is difficult to clean after polishing, and magnetic particles are clogged in minute gaps and cannot be removed.

  In the polishing by MRF, ferromagnetic magnetic particles are strongly fixed in a needle shape by a magnetic field to form a so-called magnetic cluster, and polishing is performed by pressing abrasive grains against the polishing surface by this magnetic cluster. Difficult, deep scratch marks are easily formed on the surface to be polished, and there is room for improvement in application to fine finishing.

  Incidentally, the magnetic polishing liquid contains a solvent as a composition, and the solvent is added to improve the mixing property of each composition and to add a lubricating action. Therefore, the solvent is not particularly limited as long as it can be mixed with other compositions, and in general, kerosene, silicone oil, vegetable oil, alcohol and the like are often used. However, when an organic solvent is used, there is a problem that an explosion-proof structure or local exhaust is required to prevent flammability and flammability. Therefore, the equipment cost is increased, and restrictions are increased from the viewpoint of environmental safety.

  The object of the present invention is to solve the above-mentioned problems. The object of the present invention is to adopt a composition containing water as a solvent in order to make it more advantageous in terms of environmental safety, and there is no interference with other compositions and the stability of the dispersed state. Therefore, it is an object of the present invention to provide a magnetic polishing liquid that has a high polishing ability and can obtain a good polishing ability.

  In order to achieve the above-described object, the magnetic polishing liquid according to the present invention is present around the polishing bite facing the object to be polished in a non-contact manner for fluid polishing, and is magnetically linked by the action of a magnetic field. The composition includes at least four components of magnetic particles, abrasive particles, resin particles, and a solvent, the solvent is water, and the resin particles are formed from a resin material that is not dissolved in the solvent.

  And it is good to add polyhydric alcohols, such as glycerol, as an additive which improves drying suppression and the stability of a dispersed state. Moreover, it is preferable to mix the magnetic polishing liquid with a rust preventive agent that suppresses rust on the object to be polished and the polishing apparatus. Further, the magnetic particles are preferably formed from a magnetic material having oxidation resistance to water, and are formed from a magnetic material having a saturation magnetization of 7 kG or more in volume magnetization, and specifically, the magnetic particles are formed from cobalt. Is preferred. Furthermore, the magnetic particles are preferably non-spherical particles.

  In the present invention, since water is used as a solvent, it is not flammable, it is not necessary to provide an explosion-proof structure or local exhaust equipment, and the equipment cost is reduced, and it is also preferable from the viewpoint of environmental safety. In the present invention, when a magnetic field is applied, the magnetic particles adsorb each other, and at this time, resin particles that are insoluble in water exist between the magnetic particles. When the polishing tool is interlocked with the movement of the polishing tool, the resin particles are elastically deformed, so that the processing pressure in fluid polishing is reduced, and the resin particles exhibit the function of an elastic member. As a result, scratches are less likely to occur.

  The resin particles are dispersed and sandwiched between the respective compositions, and the aggregate (magnetic cluster) of the magnetic particles is swollen as a whole. That is, the resin particles exhibit the function of a spacer member that increases the bulk of the entire magnetic cluster. Accordingly, the magnetic cluster has a large protrusion from the magnetic field generation source side, and the interval between the polishing tools can be set wide with respect to the object to be polished, thereby increasing the convenience of magnetic polishing. In this case, since the resin particles are formed from a resin material that does not dissolve in the solvent, there is no interference with water as the solvent, the polishing ability can be obtained well, and highly accurate surface polishing can be performed. It should be noted that α cellulose which has been generally used conventionally cannot be used because it dissolves in water.

  When a polyhydric alcohol such as glycerin is added as an additive, evaporation can be suppressed and the stability of the dispersed state can be improved. Moreover, since a rust inhibitor is added, rusting of the polishing object and the polishing apparatus can be prevented.

  When the magnetic particles are formed of a magnetic material having oxidation resistance to water, and the magnetic material is a magnetic material having a saturation magnetization of 7 kG or more in volume magnetization, it is possible to prevent deterioration of the polishing characteristics of the magnetic polishing liquid, High polishing ability can be obtained.

  When the magnetic particles are made into a non-spherical particle shape, when a magnetic field is applied, an aggregate having a space is formed, and water is easily absorbed. Accordingly, the water absorption is increased and moisture is easily retained and precipitation due to gravity is difficult to occur, so that a highly stable magnetic polishing liquid in a dispersed state can be obtained. At this time, since an organic dispersant is not used, environmental safety is not impaired.

  In the magnetic polishing liquid according to the present invention, when the polishing tool is interlocked with the movement of the polishing tool, the resin particles are elastically deformed to exhibit the function of the elastic member, and as a result, scratches are less likely to occur. In addition, the resin particles are dispersed and sandwiched between the respective compositions, exhibit the function of a spacer member that increases the bulk of the magnetic particle aggregate (magnetic cluster), and the overhang from the magnetic field generation source side is large. Thus, the interval between the polishing tools can be set wide with respect to the object to be polished, and the convenience of magnetic polishing is increased.

  Since the resin particles are formed from a resin material that does not dissolve in the solvent, there is no interference with water, which is the solvent, the stability of the dispersed state is high, the polishing ability can be obtained well, and highly precise surface polishing is achieved. Yes.

  FIG. 1 shows a preferred embodiment of the present invention. In this embodiment, the configuration for performing magnetic polishing includes a polishing bit 2 having a magnetic field generation source (20), the polishing object 1 is fixed to the y-axis stage 3, and the polishing bit 2 is not in contact with the polishing object 1. The magnetic polishing liquid 4 is present between the polishing object 1 and the magnetic polishing liquid 4 is mixed with abrasive particles, and the polishing tool 2 is connected to a driving means 5 associated therewith. By starting, a predetermined motion operation is performed, and by starting the y-axis stage 3, the polishing object 1 is caused to perform a predetermined motion operation on the y-axis, and fluid polishing is performed by the magnetic cluster generated in the magnetic polishing liquid 4. Is supposed to do.

  The polishing tool 2 is provided with a permanent magnet 20 at its tip to serve as a magnetic field generation source. The magnetic field generation source is not limited to the permanent magnet 20, and for example, an electromagnet can be preferably applied as long as it can act on the magnetic polishing liquid 4. The generation of the magnetic field does not have to be stationary in time, and a magnetic field that varies in time may be generated.

  The driving means 5 has a multi-axis control function for at least the x-axis and z-axis. When the driving means 5 is activated, the polishing tool 2 rotates and moves in a predetermined manner with respect to the x-axis and z-axis. Let the action take place. As the driving means 5, for example, an NC machine tool may be used, and the shaft portion of the polishing tool 2 is attached to and detached from a rotating shaft (chuck portion) such as a drilling machine, a lathe, an NC lathe, or a milling machine.

  FIG. 2 is an explanatory view schematically showing a magnetic polishing liquid according to the present invention, showing a state in which a magnetic field acts, and showing a so-called magnetic cluster.

  The magnetic polishing liquid 4 includes at least four components of magnetic particles 41, polishing particles 42, resin particles 43, and a solvent 44. The solvent 44 was water. The resin particles 43 were formed from a resin material that did not dissolve in the solvent. And you may add polyhydric alcohols, such as glycerol, as an additive which improves drying control and stability of a dispersion state. The magnetic polishing liquid 4 may be mixed with a rust preventive agent that suppresses rust on the polishing object 1 and the polishing apparatus. For example, an anionic surfactant is used as the rust inhibitor, and an appropriate amount that does not adversely affect the polishing ability is added. This magnetic polishing liquid 4 is supplied by a supply means between the polishing object 1 and the polishing bit 2.

  In the present invention, since the solvent 44 is water, the magnetic particles 41 are preferably formed of a magnetic material having oxidation resistance to water, and are formed of a magnetic material having a saturation magnetization of 7 kG or more in volume magnetization (4πM). ing. Specifically, the magnetic particles are preferably formed from cobalt, and the magnetic particles 41 are preferably aspherical particles.

  The magnetic particles 41 may have an average particle diameter of 0.01 μm to 100 μm, more preferably 0.5 μm to 10 μm. This is because when the average particle size is excessively small, the response due to the magnetic field becomes extremely weak and polishing becomes impossible. Conversely, when the particle size is excessively large, the stability of the dispersion state is deteriorated and it becomes difficult to control the polishing. .

  As the magnetic particles 41, a magnetic material that is disadvantageous in terms of oxidation resistance to water, such as iron or an iron-based alloy, can be used. In other words, such a magnetic material may be used without any inconvenience, for example, by covering the surface so as not to react with water and by taking appropriate measures for water resistance and oxidation resistance.

  The abrasive particles 42 are made of, for example, alumina, diamond, cerium oxide, silicon carbide, or the like, and have an average particle diameter of 0.01 μm to 300 μm. The particle diameter and type of the abrasive particles 42 may be appropriately changed and set according to the material and surface roughness of the object 1 to be polished, and commercially available materials can be used as raw materials.

  The resin particles 43 are formed of a resin material that does not dissolve in the solvent 44, and have an average particle diameter of several μm to several hundreds of μm. The shape of the resin particles 43 may be, for example, a spherical shape, or may be formed in a non-spherical shape such as a fibrous shape. Examples of resin materials that do not dissolve in water include polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polyvinyl chloride (PVC).

  The movement operation of the polishing tool 2 is, for example, an operation of scanning the entire surface of the polishing object 1 or a predetermined movement of the polishing object 1 with respect to the xy plane by setting the operation of the y-axis stage 3 and the driving means 5. An operation may be performed. At this time, the magnetic polishing liquid 4 is supplied to the periphery of the polishing tool 2, and the polishing tool 2 is caused to perform a rotating operation that reverses forward and backward in the axial direction. Or it is good also to perform the vibration operation | movement which vibrates predetermined.

  A magnetic polishing liquid 4 exists between the polishing tool 2 and the polishing object 1, and the magnetic polishing liquid 4 includes abrasive particles 42, and the permanent magnet 20 changes the magnetic polishing liquid 4 to be constant or variable in time. When a magnetic field is applied, a magnetic cluster is generated. That is, a large number of magnetic particles 41 in the magnetic polishing liquid are aggregated by the magnetic attractive force to form a magnetic class. Since the magnetic class is along the magnetic flux, a large number of needles are arranged in opposition to the object 1 to be polished, whereby the abrasive particles 42 present in the magnetic polishing liquid are held down on the surface of the object 1 to be polished. At this time, since the polishing tool 2 and the polishing object 1 move relative to each other, the abrasive particles 42 move while contacting the surface of the polishing object 1 to perform cutting (grinding).

  When a magnetic field is applied to the magnetic polishing liquid 4, the magnetic particles 41 adsorb each other as shown in FIG. 2, and at this time, resin particles 43 exist between the magnetic particles 41. When interlocking with the movement of the polishing tool 2, the resin particles 41 are elastically deformed, so that the processing pressure in fluid polishing is reduced and the resin particles 43 exhibit the function of an elastic member. As a result, scratches are less likely to occur.

  The resin particles 43 are present in a state of being dispersed and sandwiched between the respective compositions, and the aggregate (magnetic cluster) of the magnetic particles 41 is swollen as a whole. That is, the resin particle 43 expresses the function of a spacer member that increases the bulk of the entire magnetic cluster. Therefore, the magnetic cluster has a large protrusion from the magnetic field generation source side, and the interval between the polishing tools 2 can be set wider with respect to the object 1 to be polished, thereby increasing the convenience of magnetic polishing.

  In this case, since the resin particles 43 are formed from a resin material that does not dissolve in the solvent 44, there is no interference with the water that is the solvent 44, a good polishing ability can be obtained, and highly precise surface polishing can be performed.

  Since the solvent 44 is water and no organic solvent is used, an explosion-proof structure and local exhaust are not required, which is advantageous in terms of environmental safety. Since a polyhydric alcohol such as glycerin is added as an additive, evaporation can be suppressed and the stability of the dispersed state can be improved. Moreover, since a rust inhibitor is added, rusting of the polishing object 1 and the polishing apparatus can be prevented.

  Further, the magnetic particles 41 are formed of a magnetic material having oxidation resistance to water, and the magnetic material is a magnetic material having a saturation magnetization of 7 kG or more in volume magnetization (4πM), so that the polishing characteristics of the magnetic polishing liquid are deteriorated. Can be prevented, and a high polishing ability can be obtained.

  Here, since the magnetic particle 41 has a non-spherical particle shape, when a magnetic field is applied, an aggregate having a space is formed and water is easily absorbed. Accordingly, the water absorption is increased and moisture is easily retained and precipitation due to gravity is difficult to occur, so that a highly stable magnetic polishing liquid in a dispersed state can be obtained. At this time, since an organic dispersant is not used, environmental safety is not impaired.

  The sample was polished according to the configuration for magnetic polishing shown in FIG. That is, in order to demonstrate the effect of the present invention on the polishing ability, a plurality of magnetic polishing liquids having different compositions are prepared, the sample is polished with each magnetic polishing liquid, and the surface roughness Ra (arithmetic average roughness) after polishing is prepared. And Ry (maximum roughness).

  The composition of the magnetic polishing liquid was carbonyl iron having a particle diameter of about 1 μm, alumina abrasive grains having a particle diameter of about 3 μm, PMMA particles having a particle diameter of 20 μm, and water in the wt% shown in Table 1, and glycerin in water. 6 types from No1 to No6 were prepared by adding them at a mixing ratio of 5% and mixing them uniformly.

  The sample (polishing object 1) was a circular plate having an outer diameter of 30 mm and a thickness of 1 mm formed from stainless steel (SUS304), and the surface was polished. This polishing object 1 is caused to perform a circular motion on the xy plane, which is a motion motion of 60 rpm with a radius of 20 mm according to the operation settings of the y-axis stage 3 and the driving means 5. A neodymium magnet was used as the permanent magnet 20 of the magnetic field generation source. The rotation of the polishing tool 2 was set at 500 rpm and the polishing time was 30 minutes. The surface roughness was measured by a surface roughness level meter, and P-10 manufactured by Tencor Corporation was used for this.

When the sample was polished, the results shown in Table 1 were obtained.

  As is clear from Table 1, when the resin particle component is small (No 2), the polishing ability is reduced when the interval between the sample and the polishing tool is widened, but when the resin particle component is increased ( In No. 6), even if the distance between the sample and the polishing tool is widened, the polishing ability is hardly reduced. That is, as the resin particle component increases, magnetic polishing can be performed well even when the distance between the sample and the polishing bit is increased, and the resin particles express the function of the spacer member. . And since the resin particle expressed the function of the elastic member, it confirmed that it exists in the tendency for surface roughness to improve.

  Next, in order to demonstrate the effect of the present invention on the degree of magnetization, the polishing ability, and the stability of the dispersed state, a plurality of magnetic polishing liquids having different compositions with respect to the type of magnetic particles are prepared, and the sample is polished to obtain the surface roughness. Ra (arithmetic mean roughness) and Ry (maximum roughness) were evaluated.

  The composition of the magnetic polishing liquid was 50 wt% for magnetic particles, 20 wt% for abrasive particles, 6 wt% for resin particles, and 24 wt% for the solvent. The magnetic particles had a particle diameter of about 1 μm, and as shown in Table 2, iron, cobalt, permalloy, sendust, MnZn ferrite, nickel, and stainless steel were used. Alumina abrasive grains with a particle size of about 3 μm are used for the abrasive particles, PMMA particles with a particle size of 20 μm are used for the resin particles, the solvent is water, and glycerin is added in a ratio of 5% to water. These were prepared by mixing them uniformly.

  The sample (polishing object 1) was a circular plate having an outer diameter of 30 mm and a thickness of 1 mm formed from stainless steel (SUS304), and the surface was polished. This polishing object 1 is caused to perform a circular motion on the xy plane, which is a motion motion of 60 rpm with a radius of 20 mm according to the operation settings of the y-axis stage 3 and the driving means 5. A neodymium magnet was used as the permanent magnet 20 of the magnetic field generation source. The rotation of the polishing tool 2 was set at 500 rpm and the polishing time was 30 minutes. The surface roughness was measured by a surface roughness level meter, and P-10 manufactured by Tencor Corporation was used for this. Further, the degree of magnetization was measured with a vibrating sample magnetometer (VSM) with the powder as it was.

When the sample was polished, the results shown in Table 2 and Table 3 were obtained.

  As is clear from Table 2, it is clear that the polishing ability varies depending on the magnetization value of the magnetic particles. The surface roughness of iron, cobalt, permalloy, and sendust is on the order of about 10 nm. It was confirmed that the ability was obtained well.

  As is clear from Table 3, it can be seen that as the number of days after the preparation is completed, the reaction with water progresses and deteriorates, so that polishing cannot be performed, which is not preferable as a magnetic polishing liquid. As apparent from Table 3, it was confirmed that cobalt was highly stable with no deterioration in polishing ability.

  As described above, iron is not necessarily unavailable, and can be used without any inconvenience by taking appropriate measures for water resistance and oxidation resistance.

  Next, in order to verify the effect of the present invention regarding the stability of the dispersed state, a plurality of magnetic polishing liquids having different particle shapes are prepared for the magnetic particles, the sample is polished, and the surface roughness Ra (arithmetic average roughness) ), Ry (maximum roughness).

  The composition of the magnetic polishing liquid was 50 wt% for magnetic particles, 20 wt% for abrasive particles, 4 wt% for resin particles, and 26 wt% for the solvent. Cobalt is used for the magnetic particles, and as shown in Table 4 and FIG. 3, spherical particles 1 having a large particle size, spherical particles 2 having a small particle size, gourd-shaped non-spherical particles 1, and cylindrical non-spherical particles. Particle 2 was used respectively. Alumina abrasive grains with a particle size of about 3 μm are used for the abrasive particles, PMMA particles with a particle size of 20 μm are used for the resin particles, the solvent is water, and glycerin is added in a ratio of 5% to water. These were uniformly mixed to prepare 4 types. In addition, FIG. 3 has shown the image of the magnetic particle by an electron microscope (SEM: Scanning Electron Microscope).

  The sample (polishing object 1) was a circular plate having an outer diameter of 30 mm and a thickness of 1 mm formed from stainless steel (SUS304), and the surface was polished. This polishing object 1 is caused to perform a circular motion on the xy plane, which is a motion motion of 60 rpm with a radius of 20 mm according to the operation settings of the y-axis stage 3 and the driving means 5. A neodymium magnet is used as the permanent magnet 20 of the magnetic field generation source. The rotation of the polishing tool 2 is set to 500 rpm, the interval between the polishing tool 2 and the sample (polishing object 1) is 0.5 mm, and the polishing time is 30 minutes. It was. The surface roughness was measured by a surface roughness level meter, and P-10 manufactured by Tencor Corporation was used for this. The stability of the dispersed state was evaluated based on the precipitation state of the magnetic polishing liquid.

When the sample was polished, the results shown in Table 4 were obtained.

  As is apparent from Table 4, it was confirmed that the stability of the dispersed state can be enhanced by making the magnetic particles non-spherical and the polishing ability can be kept high without deterioration.

  In the present invention, since the dispersion state is highly stable and the polishing ability can be obtained satisfactorily, it is effective for precision polishing of the surface of ceramic materials, optical materials, metal materials, resin materials, etc. It can be preferably applied to polishing processing in various wafer processes.

1 is a side view showing a preferred embodiment of the present invention. It is explanatory drawing which shows typically the magnetic polishing liquid which concerns on this invention. The SEM image of a magnetic particle is shown, (a) is a spherical cobalt particle 1, (b) is a spherical cobalt particle 2, (c) is a gourd-shaped cobalt particle, (d) is a cylindrical cobalt particle Particles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing object 2 Polishing tool 20 Permanent magnet 3 Y-axis stage 4 Magnetic polishing liquid 41 Magnetic particle 42 Polishing particle 43 Resin particle 44 Solvent 5 Driving means

Claims (7)

In order to perform fluid polishing, there is a magnetic polishing liquid that is present around a polishing bite that faces non-contact with the object to be polished and is interlocked by the action of a magnetic field,
A magnetic polishing liquid comprising at least four components of magnetic particles, abrasive particles, resin particles, and a solvent, wherein the solvent is water and the resin particles are formed from a resin material that is not soluble in the solvent. 2. The magnetic polishing liquid according to claim 1, wherein a polyhydric alcohol such as glycerin is added as an additive for suppressing drying and improving the stability of the dispersed state.   The magnetic polishing liquid according to claim 1, wherein a rust preventive agent that suppresses rusting on a polishing target or a polishing apparatus is mixed with the magnetic polishing liquid.   The magnetic polishing liquid according to any one of claims 1 to 3, wherein the magnetic particles are formed of a magnetic material having oxidation resistance to water.   5. The magnetic polishing liquid according to claim 1, wherein the magnetic particles are formed of a magnetic material having a saturation magnetization of 7 kG or more in volume magnetization.   The magnetic polishing liquid according to claim 1, wherein the magnetic particles are made of cobalt. The magnetic polishing liquid according to claim 1, wherein the magnetic particles have a non-spherical particle shape.

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