An electromagnetic composite tool, an electromagnetic composite magnetic field cluster magnetorheological polishing device comprising the same and a polishing method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGDONG UNIV OF TECH
- Filing Date
- 2025-11-05
- Publication Date
- 2026-06-12
Smart Images
Figure CN121104875B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ultra-precision processing technology of semiconductor materials, and more specifically, relates to an electromagnetic composite tool, an electromagnetic composite magnetic field cluster magnetorheological polishing device including the tool, and a polishing method. Background Technology
[0002] The demand for hard and brittle materials is increasing daily due to modern industrial development. These materials, with their high strength, high hardness, low density, excellent wear resistance, corrosion resistance, and stable physicochemical properties, show great application potential in semiconductors, optical components, aerospace, and precision instruments. However, hard and brittle materials are prone to brittle fracture and surface and subsurface damage during processing, severely limiting their effectiveness in high-precision components. To achieve high-quality processing of hard and brittle materials, efficient and precise processing techniques must be developed. Magnetorheological polishing, as an advanced ultra-precision machining method, can achieve polishing effects without subsurface damage, making it particularly suitable for the final processing of complex curved surfaces and axisymmetric aspherical parts. It is widely used in optical components, semiconductor wafers, and display substrates. Although this technology has advantages unmatched by traditional polishing methods, its low polishing efficiency limits its further promotion.
[0003] To improve the processing efficiency of magnetorheological polishing, Chinese patent CN201310495066.8 discloses a magnetic field-assisted polishing processing device and method based on the principles of magnetorheological polishing and electromagnetic induction. This method aims to increase the proportion of mixed magnetic free abrasive particles participating in grinding and forming effective grinding behavior on the workpiece surface through an electromagnetic field, thereby enhancing the grinding efficiency of the mixed magnetic free abrasive particles. Although this method enhances the cutting performance of the magnetic free abrasive, the soft polishing tool moving along the polishing trajectory still cannot reach a large surface area of contact, making it difficult to guarantee processing efficiency. Chinese patent CN202310516177.6 discloses a multi-field composite non-contact polishing device and method based on the principles of magnetorheological polishing and a multi-field coupling mechanism. This method polishes the workpiece through a composite of temperature, electric, magnetic, chemical, and mechanical fields. The temperature field maintains a good shear thickening effect in the polishing fluid, the electric field prevents abrasive sedimentation, and the chemical field promotes oxidation on the workpiece surface, improving material removal rate. By applying a magnetic field between the polishing tool and the workpiece, the efficiency of magnetorheological polishing is enhanced by combining the effects of the aforementioned multiple fields. However, this non-contact polishing method requires precise control of multiple fields, which is difficult, costly, and makes it difficult to guarantee processing efficiency.
[0004] In summary, given the problems of low processing efficiency and poor surface uniformity in magnetorheological polishing technology, developing technologies with multi-physics field synergistic response capabilities is a key direction for promoting the development of high-precision manufacturing technology. Summary of the Invention
[0005] The present invention aims to design an electromagnetic composite tool, an electromagnetic composite magnetic field cluster magnetorheological polishing device and polishing method comprising the tool, to overcome the shortcomings of the prior art, effectively improve workpiece processing efficiency and quality, and show broad application prospects in ultra-precision machining, multi-functional equipment, physical field control and other fields.
[0006] The electromagnetic composite tool, the electromagnetic composite magnetic field cluster magnetorheological polishing device and polishing method of the present invention have multi-field coupling characteristics of electro-magnetism-electromagnetism, which can realize rapid forming and structural reorganization of magnetorheological polishing pads under the action of electromagnetic field and magnetic field, and improve the shear yield stress of magnetorheological polishing pads by enhancing magnetic field strength and magnetic field distribution.
[0007] Specifically, the electromagnetic composite tool of the present invention includes a tail cone, a tool holder, a tool flange, a clamping flange, a grooved ring, a battery, a screw, a left lead wire, a baffle, a ring-shaped permanent magnet, a sliding switch, a coil, and a workpiece disk; the tail cone, tool holder, tool flange, and clamping flange are connected in sequence; the tool holder is threaded to the tail cone, the tool flange is threaded to the tool holder, and the clamping flange is bolted to the tool flange; the grooved ring is coaxially placed on the clamping flange; the battery is installed in the groove of the clamping flange; the screw is threaded to the internal thread of the groove of the clamping flange; one end of the left lead wire is connected to the positive terminal of the battery, and the other end is connected to the terminal block a welded on the grooved ring; one end of the right lead wire is connected to the negative terminal of the battery, and the other end is connected to the terminal block b welded on the grooved ring; the baffle is threaded to the screw and moves; the ring-shaped permanent magnet is coaxially arranged with the screw; the ring-shaped permanent magnet is fixed and its position is changed by the upper and lower baffles; the sliding switch moves along the groove.
[0008] Furthermore, the left interface of the coil is connected to terminal block a, and the right interface is connected to terminal block c. The sliding switch drives terminal block c to move along the groove. When it moves to the upper limit, terminal block c contacts terminal block b, and the current is transmitted through the right wire to terminal blocks b and c, and then to the coil, thereby generating an electromagnetic field. When it moves to the lower limit, the connection between the terminal blocks is broken, and the current can no longer be transmitted, achieving circuit breaking after the work is completed. When the working condition does not require the use of a ring permanent magnet to generate a strong magnetic environment, the ring permanent magnet can be disassembled sequentially in axial order. The workpiece is processed by attaching paraffin wax to the workpiece disc. The workpiece disc and the screw are connected by threads to press the grooved ring. Sealing rings are set on the workpiece disc, grooved ring, and fixture flange to prevent magnetorheological polishing fluid from seeping into the grooved ring through gaps during tool processing due to high speed, which would damage the battery power and the conductor conductivity.
[0009] Furthermore, the left and right wires and the coil are fixed inside the wire groove ring. The coil is arranged coaxially with the screw, and its inner diameter is larger than the outer diameter of the baffle and the annular permanent magnet. The annular permanent magnet is locked by the opposing action of the upper and lower baffles, which maintains the stability of the circuit and the permanent magnet during the high-speed rotation of the cutter body, avoiding the situation where the wires fall off and the permanent magnet collides and vibrates, affecting the processing effect.
[0010] Furthermore, the toroidal permanent magnet generates magnetic fields of varying magnitudes by changing its material and position, while the coil influences electromagnetic induction by altering the type and stacking of the batteries.
[0011] The material of the toroidal permanent magnet affects the strength of the generated magnetic field. Based on the magnetic field strength, they can be classified as ferrite, AlNiCo, FeChCrCo, SamariumCo, and NdFeB, from weakest to strongest. The toroidal permanent magnet is locked to the screw by the opposing action of two layers of baffles. By changing the connection position of the upper and lower baffles with the screw, the position of the toroidal permanent magnet can be changed. The closer the toroidal permanent magnet is to the workpiece disk, the greater the magnetic flux density on the workpiece surface; the farther away from the workpiece disk, the smaller the magnetic flux density on the workpiece surface.
[0012] Based on the magnitude of the current generated, batteries can be classified from small to large as CR2430, CR2335, CR2450, CR3032, and CR2477. The larger the current, the stronger the electromagnetic induction effect of the coil. Batteries can be stacked in series, with the negative terminal of one battery in contact with the positive terminal of another. The voltage of the battery pack after series connection doubles, the current flowing through the coil increases, and the electromagnetic induction effect is enhanced.
[0013] This invention also provides an electromagnetic composite magnetic field cluster magnetorheological polishing device, including a polishing disc, a turntable, magnetic pole discs, cylindrical clustered permanent magnets, a support base, a drive disc, a base, a machine tool spindle, an XY precision moving platform, and the electromagnetic composite tool as described above. The electromagnetic composite tool is pneumatically clamped onto the machine tool spindle, which moves in the Z direction. The cylindrical clustered permanent magnets are fixed within the magnetic pole discs to generate a magnetic field and are placed together within the support base, which is fixed onto the base. The base is fixed onto the XY precision moving platform. The relative position between the workpiece disc and the polishing disc is precisely adjusted using the XY precision moving platform. Several N52 cylindrical permanent magnets are nested within the magnetic pole discs, and several magnetic pole discs are nested within the turntable.
[0014] Furthermore, the motor transmits torque to the drive disk via belt drive, the polishing disk is loaded with magnetorheological polishing fluid, the turntable is driven to rotate by the drive disk, and the bolt connection transmits torque to the polishing disk. The rotation of the polishing disk drives the polishing fluid to perform circular motion.
[0015] The present invention also provides a polishing method for the electromagnetic composite magnetic field cluster magnetorheological polishing device as described above, comprising the following steps:
[0016] Step S1: Select one of the following as the magnetic field generating device: electromagnetic field, permanent magnet magnetic field, or a composite magnetic field generating device of electromagnetic field and permanent magnet magnetic field;
[0017] Different magnetic fields can be used for different working conditions. When the workpiece has low hardness, a coil can be used to generate the magnetic field. When the workpiece has moderate hardness, a ring-shaped permanent magnet can be used to generate the magnetic field. When the workpiece has high hardness, a coil and a ring-shaped permanent magnet can be used together to generate the magnetic field. After the electromagnetic field and the magnetic field generated by the permanent magnet are superimposed, the magnetic flux density is enhanced and the uniformity of the magnetic field distribution is improved.
[0018] Step S2: After adjusting the magnetic field generating device of the electromagnetic composite tool according to the required working conditions, install the electromagnetic composite tool in the machine tool spindle, adjust the position of the XY precision moving platform after installation, and move it to the coordinate origin;
[0019] Step S3: After a series of steps such as stirring and ultrasonication, the prepared magnetorheological polishing slurry is poured into the polishing disc;
[0020] Step S4: Adjust the working gap between the workpiece disk and the polishing disk through the machine tool spindle so that the magnetorheological polishing pad under magnetic field coupling can be formed smoothly;
[0021] The abrasive is held by a magnetic chain and moves relative to the workpiece to remove material. The bundled magnetic chains form a magnetorheological flexible polishing pad under the action of a magnetic field. After introducing an external magnetic field, changing the processing gap can change the magnetic flux density on the workpiece surface, improve the magnetization state of the magnetic particles in the magnetorheological polishing pad under the coupled magnetic field, and thus improve the mechanical properties of the magnetorheological polishing pad under magnetic field coupling, so as to promote the smooth formation of the magnetorheological polishing pad under magnetic field coupling.
[0022] Step S5: Start the motor. The polishing disc rotates at a speed of 30~45r / min. After the polishing disc rotates for 5~10s, the magnetorheological fluid will form a dynamic flexible polishing pad under the action of the magnetic field. After the polishing pad rotates for 5~10s, start the polishing program. The XY precision moving platform drives the electromagnetic composite magnetic field polishing device to the processing position. The machine tool spindle drives the electromagnetic composite tool to 1mm above the polishing disc and rotates at 400~600r / min to process the surface of the workpiece.
[0023] This invention utilizes an external magnetic field generating device to couple magnetic fields with the cluster of permanent magnets inside the polishing disc. Under the action of a strong magnetic field, the magnetorheological fluid forms a thicker magnetic chain. As the polishing disc rotates, it changes the real-time morphology of the magnetorheological polishing pad, thereby improving processing efficiency and processing quality.
[0024] Furthermore, when machining soft materials with a hardness <1200HV, a coil is used to generate a magnetic field, with a machining gap of 1.2~1.5mm; when machining materials with a hardness of 1200~2000HV, a ring-shaped permanent magnet is used to generate a magnetic field, with a machining gap of 1~1.2mm; when machining materials with a hardness >2000HV, a coil and a ring-shaped permanent magnet are used together to generate a magnetic field, with a working gap of 0.8~1mm.
[0025] Furthermore, when machining soft materials with a hardness <1200 HV, such as single-crystal Si with a hardness of 1100~1300 HV, a coil can be used to generate a magnetic field. When machining materials with a moderate hardness of 1200~2000 HV, such as gallium nitride (GaN) with a hardness of 1400~1800 HV, a ring permanent magnet can be used to generate a magnetic field. When machining materials with a hardness >2000 HV, such as single-crystal SiC with a hardness of 2200~2800 HV, a coil and a ring permanent magnet can be used together to generate a magnetic field, thereby enhancing the material removal rate and improving the machining efficiency.
[0026] The machining clearance affects the relative motion between the abrasive and the workpiece, increasing the normal pressure and shear force on the workpiece surface. A lower clearance generates greater polishing force, resulting in better cutting performance and stronger cutting ability. However, increased abrasive indentation depth can cause some damage to the workpiece surface. Therefore, when machining soft materials with a hardness <1200 HV, a larger clearance (1.2~1.5 mm) is used, such as for single-crystal Si with a hardness of 1100~11300 HV, to effectively suppress surface damage while achieving good material removal. When machining materials with a moderate hardness of 1200~12000 HV, a medium clearance (1~1.2 mm) is used, such as for gallium nitride (GaN) with a hardness of 1400~11800 HV, to ensure machining efficiency while achieving good results. For machining materials with a hardness >2000 HV, a larger clearance (1~1.2 mm) is used. For materials with high hardness (HV), a lower working gap (0.8~1mm) is used, such as single-crystal SiC with a hardness of 2200~2800HV, to enhance material removal rate and improve processing efficiency.
[0027] Furthermore, during the rotation of the polishing disc, the magnetorheological polishing pad periodically acts on the workpiece surface. Under the influence of the applied magnetic field, the magnetorheological polishing pad is in a state of alternating change and restoration. This dynamically changing magnetorheological polishing pad promotes the renewal and self-sharpening of the abrasive.
[0028] The present invention also provides another polishing method for the electromagnetic composite magnetic field cluster magnetorheological polishing device as described above. The processing adopts a staged processing. In the first 2 / 3 processing stage, the magnetic field generated by the coil and the ring permanent magnet is used for rough processing. In the last 1 / 3 processing stage, the power supply to the coil is cut off by the sliding switch, and the magnetic field generated by the ring permanent magnet is used only for fine processing.
[0029] Furthermore, the wafer is processed for 120 minutes. In the first 80 minutes of the processing stage, a magnetic field is generated by the coil and the ring permanent magnet for rough processing. In the last 40 minutes of the processing stage, the power supply to the coil is cut off by a sliding switch, and the magnetic field is generated only by the ring permanent magnet for fine processing.
[0030] Introducing an electromagnetic composite tool generates an external magnetic field, increasing the magnetic flux density of the magnetorheological polishing pad under the influence of clustered permanent magnets, improving the magnetic field distribution of the polishing pad, and enhancing its mechanical properties. Depending on the orientation of the clustered permanent magnets, the introduced external magnetic field will form different composite magnetic fields. When the clustered permanent magnets are arranged in an alternating pattern, a composite interactive magnetic field will be formed. When the clustered permanent magnets are arranged in the same direction and their magnetic poles are opposite to the external magnetic field, a composite attractive magnetic field will be formed. When the magnetic poles are in the same direction as the external magnetic field, a composite repulsive magnetic field will be formed.
[0031] The attractive magnetic field enhances the magnetorheological polishing pad's ability to hold abrasive particles, improving its effect on the workpiece surface and resulting in better surface quality and uniformity. The repulsive magnetic field enhances the magnetorheological polishing pad's ability to carry abrasive particles, strengthening the magnetorheological polishing force and achieving a higher material removal rate.
[0032] Magnetorheological fluids can generate magnetic flux chains of different shapes in different magnetic field environments, thereby forming different magnetorheological dynamic flexible polishing pads. The higher the magnetic field strength, the stronger the magnetic flux chains, the greater the yield stress of the polishing pad, and the stronger the removal force on the workpiece.
[0033] Compared with the prior art, the beneficial effects of the present invention are:
[0034] The strong coupled magnetic field generated by this invention changes the clamping ability of the magnetic chain string on the abrasive, improves the mechanical properties of the magnetorheological polishing pad, strengthens the shear yield stress of the magnetorheological polishing pad, increases the polishing force on the workpiece surface, and the magnetorheological polishing pad is in a dynamic process. The processed abrasive will be re-clamped as the polishing disc rotates, which enhances the self-sharpening and renewal ability of the abrasive, reduces processing unevenness, and improves processing efficiency.
[0035] This invention can use magnetic fields of different intensities to process workpieces with different hardness. By increasing or decreasing the type of magnetic field generating device and changing the magnitude of the generated magnetic field strength, it can be adapted to different processing environments. Compared with processing multiple magnetic field generating device frames, the magnetic field generating device of this invention is versatile and shares a single outer frame structure, which reduces the device manufacturing cost, simplifies the processing flow, and improves processing efficiency. Attached Figure Description
[0036] Figure 1This is a schematic diagram of the electromagnetic composite tool of the present invention and the electromagnetic composite magnetic field cluster magnetorheological polishing device including the present invention.
[0037] Figure 2 This is a schematic diagram of the polishing method of the electromagnetic composite magnetic field cluster magnetorheological polishing device of the present invention;
[0038] Figure 3 (a) is a schematic diagram of the composite magnetic field generating device of the present invention, and (b) is a circuit diagram of the composite magnetic field generating device.
[0039] Figure 4 (a) is a schematic diagram of the electromagnetic field generating device of the present invention, and (b) is a schematic diagram of the permanent magnet magnetic field generating device of the present invention.
[0040] Figure 5 This is a schematic diagram of the electromagnetic composite tool structure of the present invention;
[0041] Figure 6 (a) is a simulation result characterization diagram of the electromagnetic composite tool and cluster magnetorheological polishing device of the present invention, and (b) is a polishing result characterization diagram of the electromagnetic composite magnetic field cluster magnetorheological polishing device including the electromagnetic composite tool.
[0042] In the diagram: 1-tail cone; 2-tool holder; 3-tool flange; 4-clamp flange; 5-groove ring; 6-battery; 7-screw; 8-left lead wire; 9-baffle; 10-ring permanent magnet; 11-slide switch; 12-coil; 13-workpiece disc; 14-workpiece; 15-polishing disc; 16-turntable; 17-magnetic pole disc; 18-cylindrical cluster permanent magnet; 19-support base; 20-drive disc; 21-base; 22-machine tool spindle; 23-XY precision moving platform; 24-right lead wire. Detailed Implementation
[0043] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.
[0044] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.
[0045] Example 1
[0046] like Figure 1 , Figure 3-5 As shown, this embodiment provides an electromagnetic composite tool, including a tail cone 1, a tool holder 2, a tool flange 3, a clamping flange 4, a grooved ring 5, a battery 6, a screw 7, a left lead wire 8, a baffle 9, a ring-shaped permanent magnet 10, a sliding switch 11, a coil 12, and a workpiece disk 13. The tail cone 1, tool holder 2, and tool flange 3 form the tool body structure; the clamping flange 4, grooved ring 5, and workpiece disk 13 form the outer frame structure of the magnetic field generating device; the battery 6, left lead wire 8, sliding switch 11, and coil 12 form the electromagnetic field generating device structure; and the screw 7, baffle 9, and ring-shaped permanent magnet 10 form the permanent magnet magnetic field generating device structure. The tool body structure, the outer frame structure of the magnetic field generating device, and the permanent magnet magnetic field generating device structure are assembled in a coaxial sequence according to the tool body structure - outer frame structure of the magnetic field generating device - magnetic field generating device structure. The assembled structure does not shift, and there is no vibration during rotation that affects the processing effect.
[0047] The tool holder 2 is threadedly connected to the tail cone 1. The tool flange 3 is threadedly connected to the tool holder 2. The clamp flange 4 is bolted to the tool flange 3. The wire groove ring 5 is placed coaxially on the clamp flange 4. The battery 6 is installed in the groove of the clamp flange 4. The screw 7 is threadedly connected to the internal thread of the groove of the clamp flange 4. One end of the left wire 8 is connected to the positive terminal of the battery 6, and the other end is connected to the terminal block a welded on the wire groove ring 5. One end of the right wire 24 is connected to the negative terminal of the battery 6, and the other end is connected to the terminal block b welded on the wire groove ring 5. The baffle 9 moves on the screw 7 through a threaded connection. The annular permanent magnet 10 is arranged coaxially with the screw 7. The annular permanent magnet 10 is fixed and its position is changed by the upper and lower baffles 9. The sliding switch 11 moves along the slide.
[0048] The left interface of coil 12 is connected to terminal block a, and the right interface is connected to terminal block c. The sliding switch 11 drives terminal block c to move along the groove. When it moves to the upper limit, terminal block c contacts terminal block b. Current is transmitted through the right wire to terminal blocks b and c, and then to coil 12, thereby generating an electromagnetic field. When it moves to the lower limit, the connection between the terminal blocks is broken, and the current cannot be transmitted, thus achieving circuit breaking after the work is completed. When the working condition does not require the use of the ring permanent magnet to generate a strong magnetic environment, the ring permanent magnet 10 can be disassembled in axial order. The workpiece disk 13 and the screw 7 are connected by threads to press the groove ring 5. The workpiece 14 is processed by attaching paraffin to the workpiece disk 13. Sealing rings are set on the workpiece disk 13, the groove ring 5, and the clamping flange 4 to prevent the magnetorheological polishing fluid from seeping into the groove ring 5 through the gaps during tool processing due to high speed, which would damage the battery power and the conductor conductivity.
[0049] The left wire 8, the right wire 24, and the coil 12 are fixed inside the wire groove ring 5. The coil 12 is arranged coaxially with the screw 7, and its inner diameter is larger than the outer diameter of the baffle 9 and the annular permanent magnet 10. The annular permanent magnet 10 is locked by the opposing action of the upper and lower baffles 9, which maintains the stability of the circuit and the permanent magnet during the high-speed rotation of the cutter body, and avoids the situation where the wire falls off and the permanent magnet collides and vibrates, affecting the processing effect.
[0050] The annular permanent magnet 10 generates magnetic fields of varying magnitudes by changing its material and position. The material of the annular permanent magnet 10 affects the strength of the generated magnetic field, and they can be classified into ferrite, AlNiCo, FeChCrCo, SamariumCo, and NeodymiumFeB according to their magnetic field strength from smallest to largest. The annular permanent magnet 10 is locked to the screw 7 by the opposing action of two layers of baffles 9. By changing the connection position between the upper and lower layers of baffles 9 and the screw 7, the position of the annular permanent magnet 10 can be changed. The closer the annular permanent magnet 10 is to the workpiece disk, the greater the magnetic flux density on the workpiece surface; the farther away from the workpiece disk, the smaller the magnetic flux density on the workpiece surface.
[0051] Coil 12 influences the electromagnetic induction effect by changing the type and stacking method of the batteries. Based on the magnitude of the generated current, the batteries can be categorized from smallest to largest as CR2430, CR2335, CR2450, CR3032, and CR2477. The larger the current, the stronger the electromagnetic induction effect of the coil. The batteries can be stacked in series, with the negative terminal of one battery in contact with the positive terminal of another. This series-connected battery pack doubles the voltage, increasing the current flowing through the coil and enhancing the electromagnetic induction effect.
[0052] Example 2
[0053] like Figure 1 , Figure 3-5As shown, this embodiment provides an electromagnetic composite magnetic field cluster magnetorheological polishing device, including a polishing disc 15, a turntable 16, a magnetic pole disc 17, cylindrical clustered permanent magnets 18, a support base 19, a drive disc 20, a base 21, a machine tool spindle 22, an XY precision moving platform 23, and the electromagnetic composite tool described in Embodiment 1. The electromagnetic composite tool is pneumatically clamped on the machine tool spindle 22, and the machine tool spindle 22 clamps the electromagnetic composite tool and moves it in the Z direction. The cylindrical clustered permanent magnets 18 are fixed in the magnetic pole disc 17 to generate a magnetic field and are placed together in the support base 19, which is fixed on the base 21. The base 21 is fixed on the XY precision moving platform 23. The relative position between the workpiece disc 13 and the polishing disc 15 is precisely adjusted by the XY precision moving platform 23. Sixteen N52 cylindrical permanent magnets with an outer diameter of 25mm and a height of 40mm are nested in the magnetic pole disc 17, and the six magnetic pole discs are arranged in a 60° circumferential array in the support base 19.
[0054] The motor transmits torque to the drive disk 20 via belt drive. The polishing disk 15 is loaded with magnetorheological polishing fluid. The turntable 16 is driven to rotate by the drive disk 20. The torque is transmitted to the polishing disk 15 via bolt connection. The rotation of the polishing disk 15 drives the polishing fluid to perform circumferential motion to polish the 2-inch single crystal Si wafer.
[0055] exist Figure 2 When the electromagnetic composite tool shown is fed axially to the terminal position to press the polishing pad, the different orientations of the magnetic poles of the clustered permanent magnets 18 within the magnetic pole disk 17 will form composite interactive magnetic fields, composite attraction magnetic fields, and composite repulsion magnetic fields. The magnitudes of the magnetic flux density modulus and the coefficient of variation on the workpiece surface change with the characteristics of the composite magnetic fields. Compared to the absence of composite magnetic fields, the magnetic flux density modulus of the three composite magnetic fields is increased, and the coefficient of variation is decreased. Figure 6 The data in (a) is based on a static composite magnetic field simulation model established by COMSOL multiphysics simulation software. The simulations of different composite magnetic fields at the processing position are compared. After the simulation is completed, the magnitude of the magnetic flux density modulus and the uniformity of the magnetic field distribution on the workpiece surface under different composite magnetic fields are recorded. The uniformity of the magnetic field distribution is characterized by the coefficient of variation. The smaller the coefficient of variation value, the closer the sample value is and the better the uniformity.
[0056] like Figure 6 As shown in (a), the magnetic flux density modulus of the composite interactive magnetic field increases the most, at 28.76%, and the coefficient of variation decreases the most, at 81.56%. This indicates that the composite interactive magnetic field, composed of the interaction of attracting and repulsive magnetic fields, has the greatest impact on the magnitude and distribution of the magnetic field on the workpiece surface.
[0057] Figure 6(b) Data: Before the experiment, the original surface roughness Sa of the single-crystal Si wafer was approximately 433 nm. After processing, the wafer was sequentially sprayed with alcohol, wiped with a wet cloth, and ultrasonically cleaned with deionized water, followed by drying to obtain a clean surface. The surface roughness after polishing was measured using an optical 3D surface profilometer (SuperView WM100, China), and five measuring points were selected on the workpiece surface as evaluation indicators. Simultaneously, the difference in wafer mass before and after processing was measured using a precision balance (GB204, China) with a measurement accuracy of 0.1 mg, and the material removal rate (MRR) was calculated accordingly.
[0058] like Figure 6 The polishing results shown in (b) indicate that the composite interactive magnetic field can achieve good surface quality (surface roughness of 4.97 nm) and high material removal rate (material removal rate of 105.93 nm / min), which is 36.69% (surface roughness) and 25% (material removal rate) higher than that without the composite magnetic field. In contrast, the composite attraction magnetic field and the composite repulsion magnetic field only improve surface roughness or material removal rate. This shows that the single attraction magnetic field or repulsion magnetic field has limitations in improving wafer processing. Combining attraction magnetic field and repulsion magnetic field can make the two magnetic fields complementary and produce the optimal processing effect.
[0059] In this embodiment, the magnetorheological polishing pad generates clustered flexible micro-grinding heads under the influence of the magnetic field generated by the internal clustered permanent magnets 18. These clustered flexible micro-grinding heads form a magnetorheological flexible polishing pad. As the electromagnetic composite tool's axial feed motion introduces an external magnetic field, the coupled magnetic field causes the magnetorheological polishing pad to change, increasing its effective range on the workpiece surface and enhancing its clamping ability for the abrasive. This, in turn, strengthens the magnitude of the magnetorheological polishing force. With the relative movement between the polishing disc and the electromagnetic composite tool, the magnetorheological polishing pad exists in both restoration and change states. The magnetorheological polishing pad is dynamically updated in real time, promoting the re-clamping of the abrasive and achieving self-sharpening renewal of the abrasive. This more effectively grinds and polishes the surface to be processed, improving the efficiency and uniformity of magnetorheological processing.
[0060] Before and after processing, a precision electronic balance (accuracy of 0.1 mg) was used to weigh the mass change of the wafer before and after polishing to calculate the material removal rate (MRR). After processing, an optical 3D surface profilometer (SuperView WM100, China) was used to measure the surface roughness Ra and morphology changes before and after polishing. For each test, five different positions on the same radius were measured and the average value was taken. The coefficient of variation was used to represent the change in roughness to evaluate the polishing effect.
[0061] Example 3
[0062] This embodiment provides a method for magnetorheological polishing of semiconductor wafers using the electromagnetic composite magnetic field cluster magnetorheological polishing device described in Embodiment 2, comprising the following steps:
[0063] Step S1: Using a 6-inch single-crystal Si wafer as the polishing target, select coil 12 to generate a magnetic field (disassemble the annular permanent magnet 10 in axial order).
[0064] Step S2: Install the electromagnetic composite tool inside the machine tool spindle 22, adjust the position of the XY precision moving platform 23 after installation, and move it to the coordinate origin;
[0065] Step S3: The magnetorheological polishing fluid is composed of 30% carbonyl iron powder, 3% diamond abrasive, and 67% deionized water. After ultrasonic stirring, it is poured into the polishing disc 15.
[0066] Step S4: Adjust the working gap between the workpiece disk 13 and the polishing disk 15 to 1.2~1.5mm using the machine tool spindle 22 so that the magnetorheological polishing pad under magnetic field coupling can be formed smoothly.
[0067] Step S5: Start the motor. The polishing disc 15 rotates at a speed of 30~40 r / min. After the polishing disc rotates for 5~10 seconds, the magnetorheological fluid will form a dynamic flexible polishing pad under the action of the magnetic field. After the polishing pad rotates for 5~10 seconds, start the polishing program. The XY precision moving platform 23 drives the electromagnetic composite magnetic field polishing device to the processing position. The machine tool spindle 22 drives the electromagnetic composite tool to 1 mm above the polishing disc and rotates at 400~500 r / min to process the surface of the workpiece.
[0068] Example 4
[0069] This embodiment provides a method for magnetorheological polishing of semiconductor wafers using the electromagnetic composite magnetic field cluster magnetorheological polishing device described in Embodiment 2, comprising the following steps:
[0070] Step S1: Select a 6-inch gallium arsenide (GaAs) wafer as the polishing object. Use only the ring permanent magnet 10 to generate a magnetic field to change the magnetic field distribution on the surface of the workpiece to be processed (the left interface of the coil 12 is connected to the terminal block a, and the right interface is connected to the terminal block c. The sliding switch 11 drives the terminal block c to move along the slide groove. When it moves to the lower limit, the connection between the terminal blocks is broken).
[0071] Step S2: Install the electromagnetic composite tool inside the machine tool spindle 22, adjust the position of the XY precision moving platform 23 after installation, and move it to the coordinate origin;
[0072] Step S3: The magnetorheological polishing fluid is composed of 35% carbonyl iron powder, 3% diamond abrasive, and 62% deionized water. After ultrasonic stirring, it is poured into the polishing disc 15.
[0073] Step S4: Adjust the working gap between the workpiece disk 13 and the polishing disk 15 to 1~1.2mm using the machine tool spindle 22 so that the magnetorheological polishing pad under magnetic field coupling can be formed smoothly;
[0074] Step S5: Start the motor. The polishing disc 15 rotates at a speed of 32.5~42.5 r / min. After the polishing disc rotates for 5~10 seconds, the magnetorheological fluid will form a dynamic flexible polishing pad under the action of the magnetic field. After the polishing pad rotates for 5~10 seconds, start the polishing program. The XY precision moving platform 23 drives the electromagnetic composite magnetic field polishing device to the processing position. The machine tool spindle 22 drives the electromagnetic composite tool to 1 mm above the polishing disc and rotates at 500~550 r / min to process the surface of the workpiece.
[0075] In this embodiment, the workpiece surface processing time is typically 120 minutes. During the initial 80-minute processing phase, the annular permanent magnet 10 is fixed near the workpiece end using upper and lower limiting baffles 9, enhancing the mechanical properties of the magnetorheological polishing pad and significantly improving the material removal rate. During the final 40-minute processing phase, the annular permanent magnet 10 is fixed further away from the workpiece end using upper and lower limiting baffles 9, weakening the mechanical properties of the magnetorheological polishing pad and preventing over-processing that could lead to a decrease in surface quality. A suitable fixing position for the annular permanent magnet is selected using a Tesla meter.
[0076] Example 5
[0077] This embodiment provides a method for magnetorheological polishing of semiconductor wafers using the electromagnetic composite magnetic field cluster magnetorheological polishing device described in Embodiment 2, comprising the following steps:
[0078] Step S1: Using a 6-inch semiconductor wafer (single-crystal SiC or gallium nitride GaN) as the processing object, the electromagnetic field generating device and the permanent magnet generating device are installed within the frame to ensure the stability of the assembly structure. After the workpiece 14 to be processed is attached to the workpiece disk 13, the electromagnetic composite magnetic field generating device is connected to the tool body structure. The magnetic field strength on the workpiece surface is changed by replacing the high-voltage battery 6 or changing the position of the ring permanent magnet 10. After adjusting the configuration of the magnetic field generating device, the magnetic field strength on the surface of the workpiece to be processed is measured using a Tesla meter to determine whether it meets the requirements.
[0079] Step S2: Install the electromagnetic composite tool inside the machine tool spindle 22, adjust the position of the XY precision moving platform 23 after installation, and move it to the coordinate origin;
[0080] Step S3: The magnetorheological polishing slurry is composed of 35% carbonyl iron powder, 5% diamond abrasive and 40% deionized water. After stirring and sonicating, the prepared magnetorheological polishing slurry is poured into the polishing disc 15.
[0081] Step S4: Adjust the working gap between the workpiece disk 13 and the polishing disk 15 to 0.8~1mm using the machine tool spindle 22 so that the magnetorheological polishing pad under magnetic field coupling can be formed smoothly.
[0082] Step S5: Start the motor. The polishing disc 15 rotates at a speed of 42.5~45 r / min. After the polishing disc rotates for 5~10 seconds, the magnetorheological fluid will form a dynamic flexible polishing pad under the action of the magnetic field. After the polishing pad rotates for 5~10 seconds, start the polishing program. The XY precision moving platform 23 drives the electromagnetic composite magnetic field polishing device to the processing position. The machine tool spindle 22 drives the electromagnetic composite tool to 1 mm above the polishing disc and rotates at 550~600 r / min to process the surface of the workpiece.
[0083] Before step S4, it is necessary to observe the formation state of the magnetorheological polishing pad under the coupled magnetic field. When the magnetorheological polishing pad is randomly distributed under the coupled magnetic field, the shape of the magnetorheological polishing pad is changed by adjusting the orientation of the cluster permanent magnets. After obtaining the optimal shape, the magnetic field strength at this time is measured with a Tesla meter to see if it meets the requirements. If it does not meet the requirements, the configuration of the magnetic field generating device needs to be readjusted.
[0084] This invention can use magnetic fields of different intensities to process workpieces with different hardness. By increasing or decreasing the type of magnetic field generating device and changing the magnitude of the generated magnetic field strength, it can be adapted to different processing environments. Compared with processing multiple magnetic field generating device frames, the magnetic field generating device of this invention is versatile and shares a single outer frame structure, which reduces the device manufacturing cost, simplifies the processing flow, and improves processing efficiency.
[0085] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
Claims
1. An electromagnetic composite tool, characterized in that, The device includes a tail cone (1), a tool holder (2), a tool flange (3), a clamp flange (4), a wire groove ring (5), a battery (6), a screw (7), a left wire (8), a baffle (9), an annular permanent magnet (10), a sliding switch (11), a coil (12), and a workpiece disk (13); the tail cone (1), the tool holder (2), the tool flange (3), and the clamp flange (4) are connected in sequence; the wire groove ring (5) is placed coaxially on the clamp flange (4); the screw (7) is threaded to the internal thread of the groove of the clamp flange (4); one end of the left wire (8) is connected to the positive terminal of the battery (6), and the other end is connected to the terminal block a welded on the wire groove ring (5); one end of the right wire (24) is connected to the negative terminal of the battery (6), and the other end is connected to the terminal block b welded on the wire groove ring (5); the annular permanent magnet (10) is arranged coaxially with the screw (7); the sliding switch (11) moves along the groove. The left interface of the coil (12) is connected to the terminal block a, and the right interface is connected to the terminal block c. The sliding switch (11) drives the terminal block c to move along the slide groove. When it moves to the upper limit, the terminal block c contacts the terminal block b. The current is transmitted through the right wire to the terminal blocks b and c and then to the coil (12), thereby generating an electromagnetic field. When it moves to the lower limit, the connection between the terminal blocks is broken. The ring-shaped permanent magnet (10) generates magnetic fields of different magnitudes by changing its material and position, and the coil (12) affects the electromagnetic induction by changing the type and stacking method of the battery; The left conductor (8), the right conductor (24) and the coil (12) are fixed inside the groove ring (5). The coil (12) is arranged coaxially with the screw (7), and its inner diameter is larger than the outer diameter of the baffle (9) and the annular permanent magnet (10).
2. An electromagnetic composite magnetic field cluster magnetorheological polishing device, characterized in that, The assembly includes a polishing disc (15), a turntable (16), a magnetic pole disc (17), a cylindrical cluster of permanent magnets (18), a support base (19), a drive disc (20), a base (21), a machine tool spindle (22), an XY precision moving platform (23), and the electromagnetic composite tool as described in claim 1. The electromagnetic composite tool is pneumatically clamped on the machine tool spindle (22), and the machine tool spindle (22) clamps the electromagnetic composite tool and moves it in the Z direction. The cylindrical cluster of permanent magnets (18) is fixed in the magnetic pole disc (17) to generate a magnetic field, and they are placed together in the support base (19). The support base (19) is fixed on the base (21), and the base (21) is fixed on the XY precision moving platform (23).
3. The electromagnetic composite magnetic field cluster magnetorheological polishing device according to claim 2, characterized in that, The motor transmits torque to the drive disk (20) via belt drive. The polishing disk (15) is loaded with magnetorheological polishing fluid. The turntable (16) is driven to rotate by the drive disk (20). The bolt connection transmits torque to the polishing disk (15). The polishing disk (15) rotates and drives the polishing fluid to perform circular motion.
4. The polishing method of the electromagnetic composite magnetic field cluster magnetorheological polishing device according to any one of claims 2-3, characterized in that, Includes the following steps: Step S1: Select one of the following as the magnetic field generating device: electromagnetic field, permanent magnet magnetic field, or a composite magnetic field generating device of electromagnetic field and permanent magnet magnetic field; Step S2: After adjusting the magnetic field generating device of the electromagnetic composite tool according to the required working conditions, install the electromagnetic composite tool in the machine tool spindle (22), adjust the position of the XY precision moving platform (23) after installation, and move it to the coordinate origin; Step S3: Pour the magnetorheological polishing slurry into the polishing disc (15); Step S4: Adjust the working gap between the workpiece disk (13) and the polishing disk (15) by the machine tool spindle (22) so that the magnetorheological polishing pad under magnetic field coupling can be formed smoothly; Step S5: Start the motor, the polishing disc (15) rotates at a speed of 30~45r / min. After the polishing disc rotates for 5~10s, the magnetorheological fluid will form a dynamic flexible polishing pad under the action of the magnetic field. After the polishing pad rotates for 5~10s, start the polishing program. The XY precision moving platform (23) drives the electromagnetic composite magnetic field polishing device to the processing position. The machine tool spindle (22) drives the electromagnetic composite tool to 1mm above the polishing disc and rotates at 400~600r / min to process the surface of the workpiece.
5. The method according to claim 4, characterized in that: When processing soft materials with a hardness <1200HV, a coil (12) is used to generate a magnetic field, and the processing gap is 1.2~1.5mm; when processing materials with a hardness of 1200~2000 HV, a ring permanent magnet (10) is used to generate a magnetic field, and the processing gap is 1~1.2mm; when processing materials with a hardness >2000 HV, a coil (12) and a ring permanent magnet (10) are used together to generate a magnetic field, and the working gap is 0.8~1mm.
6. The method according to claim 4, characterized in that: During the rotation of the polishing disc, the magnetorheological polishing pad periodically acts on the workpiece surface. Under the influence of the external magnetic field, the magnetorheological polishing pad is in a periodic alternation state of change and recovery.
7. The method according to claim 4, characterized in that, The processing adopts a staged processing method. In the first 2 / 3 processing stage, the magnetic field generated by the coil (12) and the ring permanent magnet (10) is used for rough processing. In the last 1 / 3 processing stage, the power supply of the coil (12) is cut off by the sliding switch (11), and the magnetic field generated by the ring permanent magnet (10) is used for fine processing.