A grinding wheel and a silicon carbide electrochemical nanogrinding method using the same

Abstract

This invention discloses a grinding wheel and a silicon carbide electrochemical nanogrinding method using the same. The grinding wheel includes a grinding wheel ring, grinding wheel blocks, and an ultrasonic vibration module; multiple grinding wheel blocks are arranged at intervals at the bottom of the grinding wheel ring, and the ultrasonic vibration module is installed at the top of the grinding wheel ring; each grinding wheel block includes a core and an outer layer surrounding the core; the core has a porous structure; the outer layer is made of composite abrasive particles, active metal, carbon fiber, and a conductive binder, and the composite abrasive particles, active metal, and carbon fiber are embedded within a conductive matrix formed by the conductive binder. The grinding wheel proposed in this invention can effectively enhance the grinding force and grinding ratio of the grinding wheel, thereby significantly improving the grinding efficiency when used for electrochemical nanogrinding; on the other hand, it can significantly reduce the wear and damage of the grinding wheel during electrochemical nanogrinding, thus extending the service life of the grinding wheel.

Description

Technical Field

[0001] This invention relates to the field of electrochemical assisted machining technology, and in particular to a grinding wheel and a silicon carbide electrochemical nanogrinding method using the same. Background Technology

[0002] Electrochemical-assisted machining (EMA) is a composite machining technology that integrates electrochemical processes with traditional mechanical / physical machining. Its core principle is to alter the physicochemical properties (such as hardness, brittleness, and surface stress) of the workpiece material through electrochemical processes (e.g., anodic dissolution, passivation, surface modification), thereby reducing the difficulty of traditional machining, improving machining efficiency and surface quality, or achieving high-precision / low-damage machining that is difficult to achieve with a single machining technique. Specifically, common types of EMA include electrochemical mechanical polishing (ECMP) and electrochemical nanogrinding (ECNG).

[0003] However, current grinding wheels used in electrochemical assisted machining still suffer from several technical defects, which severely restrict grinding efficiency, machining quality, and industrial application. Specific problems are as follows:

[0004] Firstly, grinding wheels lack active catalytic design, resulting in low oxidation reaction efficiency and excessive energy consumption. Existing electrochemical grinding wheels generally use a single metal bond (such as pure copper), which only serves to fix the abrasive grains and lacks active catalytic sites for the electrochemical oxidation reaction. During grinding, because the bond cannot catalyze the formation and decomposition of the oxide film on the workpiece surface, the kinetic rate of the electrochemical oxidation reaction is slow, requiring the application of a high voltage (typically >20V) to meet the oxidation reaction requirements. However, this high voltage not only significantly increases the energy consumption of the grinding process but also leads to localized overheating damage on the workpiece surface due to enhanced Joule heating between electrodes, reducing the quality of the machined surface.

[0005] Secondly, the separation of the electrochemical activation and mechanical removal stages prevents in-situ synergy. In existing electrochemical-assisted machining technologies, the electrochemical activation stage (forming an oxide layer on the workpiece surface) and the mechanical removal stage (removing the oxide layer by abrasive grains) are usually spatially or temporally separated: some processes require offline electrochemical activation of the workpiece before transferring it to mechanical polishing equipment for removal; even in online electrochemical-assisted machining equipment, due to defects in the abrasive wheel structure design, the oxidation reaction area and the mechanical action area of ​​the abrasive grains are misaligned, making it impossible to achieve "oxidation-removal" simultaneously in the same location. This stage separation makes the oxide layer prone to secondary hardening before mechanical removal, or the abrasive action area lacking fresh oxide layer replenishment, which not only reduces material removal efficiency but also easily leads to defects such as scratches and residual oxide layers on the workpiece surface, making it difficult to achieve stable processing of a near-smooth surface.

[0006] Third, the short lifespan of grinding wheels and the need for frequent dressing severely impact the continuity of grinding efficiency. During long-term use, traditional grinding wheels suffer from several issues. First, the bonding agent (such as copper) is prone to surface passivation (forming a dense oxide film) under electrochemical conditions, leading to a rapid decline in its electrical conductivity and catalytic performance. Second, the insufficient bonding strength between the abrasive grains and the bonding agent makes them prone to premature detachment under mechanical force, resulting in a decrease in abrasive grain density on the grinding wheel surface and a weakening of cutting ability. These problems reduce the effective lifespan of the grinding wheel; furthermore, frequent dressing after passivation or abrasive grain detachment significantly reduces production continuity and overall grinding efficiency, while also increasing equipment maintenance costs.

[0007] In summary, existing electrochemical assisted machining technologies have significant shortcomings in terms of grinding wheel catalytic performance, process stage synergy, and grinding wheel durability. It is difficult to balance grinding efficiency, processing quality, and energy consumption costs. The industry urgently needs to break through existing technological bottlenecks and develop an electrochemical mechanical grinding wheel and related technologies that have high catalytic activity, can achieve in-situ synergistic polishing, and have a long lifespan. Summary of the Invention

[0008] The purpose of this invention is to provide a grinding wheel that can effectively enhance the grinding force and grinding ratio of the grinding wheel, thereby significantly improving the grinding efficiency when used for electrochemical nanogrinding. On the other hand, it can significantly reduce the wear and damage of the grinding wheel during electrochemical nanogrinding, thereby extending the service life of the grinding wheel and overcoming the shortcomings of the prior art.

[0009] Another objective of this invention is to propose an electrochemical nanogrinding method for silicon carbide using the aforementioned grinding wheel, which can significantly improve the efficiency of achieving a quasi-smooth surface on silicon carbide wafers while reducing the processing cost of silicon carbide.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] A grinding wheel includes a grinding wheel ring, grinding wheel blocks, and an ultrasonic vibration module; the grinding wheel ring is a conductive ring, multiple grinding wheel blocks are provided, and the multiple grinding wheel blocks are spaced apart at the bottom of the grinding wheel ring, and the ultrasonic vibration module is installed on the top of the grinding wheel ring, with the radiating end of the ultrasonic vibration module facing the top of the grinding wheel ring;

[0012] The grinding wheel block includes a core and an outer layer that wraps around the core;

[0013] The core has a porous structure;

[0014] The outer layer is made of composite abrasive particles, active metal, carbon fiber and conductive binder, and the composite abrasive particles, the active metal and the carbon fiber are embedded in the interior of a conductive matrix formed by curing the conductive binder.

[0015] Preferably, the raw materials of the composite abrasive include abrasive grains, ceramic binders, and nanoparticles, and the abrasive grains and nanoparticles are embedded in the interior of an adhesive matrix formed by curing the ceramic binder;

[0016] The abrasive grains have a particle size of 100 to 20,000 mesh, and the volume of the abrasive grains is 10 to 40% of the volume of the composite abrasive grains. The abrasive grains include any one or more combinations of diamond, boron carbide, silicon carbide, alumina, chromium oxide, and CeO2.

[0017] The volume of the ceramic binder is 50-85% of the volume of the composite abrasive, and the ceramic binder is a Bi2O3-B2O3 ceramic binder.

[0018] The mass of the nanoparticles is 5-10% of the mass of the ceramic binder, and the nanoparticles are nano-SiC particles or nano-ZrO2 particles.

[0019] Preferably, the active metal is a bismuth alloy or a copper alloy, and the conductive binder is a copper or titanium alloy.

[0020] Preferably, the porosity of the core is 20-30%;

[0021] The core includes a porous inner layer and a porous outer wall that wraps around the porous inner layer.

[0022] The pore size distribution of the porous inner layer is as follows: large pores account for 60-80% of the pore size structure volume, and medium pores account for 20-40% of the pore size structure volume.

[0023] The porous outer wall pore size distribution is as follows: medium pores account for 50-70% of the pore size structure volume, and large pores account for 30-50% of the pore size structure volume;

[0024] The mesopores have a particle size of 10–50 nm, and the macropores have a pore size of 100–300 μm.

[0025] Preferably, the grinding wheel block further includes an anti-passivation layer, and the anti-passivation layer is wrapped around the outside of the outer layer;

[0026] The passivation-resistant layer is a tantalum carbide layer or a graphene layer.

[0027] A silicon carbide electrochemical nanogrinding method, using the aforementioned grinding wheel, includes the following steps:

[0028] A. Fix the grinding wheel to the polishing spindle, and fix the silicon carbide wafer to be processed to the workpiece table; then, connect the negative terminal of the pulse power supply to the grinding wheel, and connect the positive terminal of the pulse power supply to the silicon carbide wafer.

[0029] The electrolyte is continuously supplied to the processing surface of the silicon carbide wafer through an electrolyte circulation system, and the processing surface of the silicon carbide wafer is completely immersed in the electrolyte.

[0030] B. Start the pulse power supply, the polishing spindle, the workpiece table and the ultrasonic vibration module, and make the grinding wheel and the silicon carbide wafer rotate relative to each other through the polishing spindle and the workpiece table;

[0031] C. The grinding wheel is fed to the silicon carbide wafer, and the grinding wheel performs electrochemical nano-grinding on the processing surface of the silicon carbide wafer.

[0032] Preferably, in step A, the electrolyte comprises any one or more combinations of NaOH, NaCl, KaCl, KNO3, ethylene carbonate, and propylene carbonate solutions, and the concentration of the electrolyte is 5-15%.

[0033] In step B, the voltage of the pulse power supply is 5-20V and the frequency is 1-10kHz.

[0034] Preferably, in step B, the polishing spindle is started and the linear velocity of the grinding wheel is set to 10-20 m / s; the workpiece stage is started and the rotational speed of the silicon carbide wafer is set to 2-5 m / s; the amplitude of the ultrasonic vibration module is 5-20 μm.

[0035] In step C, the feed speed of the grinding wheel is 0.05 to 0.2 μm / s.

[0036] Preferably, in step C, the processing temperature of the electrochemical nano-grinding is <50°C.

[0037] Preferably, step C further includes:

[0038] The processing voltage, current, and / or grinding force during the electrochemical nanogrinding process are monitored in real time, and the concentration of the electrolyte and the output parameters of the pulse power supply, the polishing spindle, the workpiece table, and / or the ultrasonic vibration module are dynamically adjusted.

[0039] The technical solution provided by this invention may include the following beneficial effects:

[0040] 1. The grinding wheel proposed in this solution has a special structure that can realize the synergistic effect of electrochemical-ultrasonic-mechanical grinding. Under the action of electrochemical corrosion, the workpiece surface material is softened by the electrolyte and generates low-hardness oxides. Combined with the mechanical removal effect of the grinding wheel and the high-frequency vibration effect of the ultrasonic vibration module, the electrolyte diffusion efficiency and oxide film removal effect are significantly improved, thereby effectively reducing the formation of subsurface damage on the workpiece surface.

[0041] 2. This solution proposes an electrochemical nano-grinding method for silicon carbide using the aforementioned grinding wheel. Thanks to the composite structure design of the grinding wheel in this solution, the proposed electrochemical nano-grinding method can achieve an organic combination of the two stages of electrochemical activity and mechanical removal, thus realizing efficient and high-quality processing of high-hardness silicon carbide materials. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of a grinding wheel according to the present invention.

[0043] Figure 2 This is a schematic diagram of the silicon carbide electrochemical nanogrinding method of the present invention.

[0044] Among them: grinding wheel 100, grinding wheel ring 1, grinding wheel block 2, core 21, outer layer 22, composite abrasive 221, active metal 222, carbon fiber 223, conductive binder 224, anti-passivation layer 23, ultrasonic vibration module 3.

[0045] 200 silicon carbide wafers;

[0046] Electrolyte circulation system 300. Detailed Implementation

[0047] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0048] This technical solution provides a grinding wheel, including a grinding wheel ring 1, grinding wheel blocks 2, and an ultrasonic vibration module 3; the grinding wheel ring 1 is a conductive ring, multiple grinding wheel blocks 2 are provided, and the multiple grinding wheel blocks 2 are spaced apart at the bottom of the grinding wheel ring 1, and the ultrasonic vibration module 3 is installed on the top of the grinding wheel ring 1, with the radiating end of the ultrasonic vibration module 3 facing the top of the grinding wheel ring 1;

[0049] The grinding wheel block 2 includes a core 21 and an outer layer 22 wrapped around the core 21.

[0050] The core 21 has a porous structure;

[0051] The outer layer 22 is made of composite abrasive particles 221, active metal 222, carbon fiber 223 and conductive binder 224, and the composite abrasive particles 221, the active metal 222 and the carbon fiber 223 are embedded in the interior of the conductive matrix formed by the conductive binder 224.

[0052] To overcome the technical deficiencies in existing technologies, this technical document proposes a grinding wheel with highly efficient catalytic activity, enabling in-situ synergistic polishing and a long lifespan, such as... Figure 1 As shown, it includes, from top to bottom, an ultrasonic vibration module 3, a conductive grinding wheel ring 1 (such as a copper metal ring), and a grinding wheel block 2 that can achieve in-situ synergistic electrochemical-mechanical grinding.

[0053] First, the grinding wheel block 2 of this solution includes a core 21 and an outer layer 22 wrapped around the core 21. The two-layer structure can achieve better material removal effect and higher processing accuracy.

[0054] Specifically, the core 21 has a porous structure. During electrochemical assisted processing, this porous structure not only helps the electrolyte to quickly penetrate into the grinding wheel, but also allows the reaction products generated during the processing to be discharged in a timely manner, thereby avoiding clogging and ensuring the continuity and efficiency of the processing.

[0055] Furthermore, the outer layer 22 is essentially a composite structure in which composite abrasive particles 221, active metal 222, and carbon fiber 223 are embedded in a conductive matrix cured by a conductive binder 224. The conductive matrix cured by the conductive binder 224 provides the structural basis for the high-efficiency electrochemical performance and mechanical stability of the grinding wheel; the addition of active metal 222 not only improves the efficiency of the electrochemical reaction between the grinding wheel and the electrolyte, but also effectively extends the service life of the grinding wheel; adding carbon fiber to the grinding wheel can produce a grinding wheel with higher strength, higher wear resistance, better heat dissipation, and better grinding performance, meeting various high-precision and high-efficiency grinding requirements. In addition, thanks to the material composition of the outer layer 22, a microchannel conductive network is formed inside the outer layer 22 of the grinding wheel block 2, which is conducive to achieving uniform current distribution and minimizing resistance loss; when applied to electrochemical nanogrinding, it can form a closed electrochemical circuit with the external power supply and the workpiece, ensuring that the grinding wheel can achieve precise control of electrochemical parameters during operation. For example, by adjusting parameters such as voltage and current density, the formation rate and thickness of the oxide film can be flexibly adjusted, thereby optimizing material removal efficiency and surface quality. It should be noted that the proportions of the raw materials in the outer layer 22 can be determined according to specific application requirements (such as high electrical and thermal conductivity requirements, high wear resistance and high strength requirements, lightweight and high strength requirements, etc.), and are not limited in this case.

[0056] Secondly, in order to improve the performance of the grinding wheel during the machining process, this solution also integrates an ultrasonic vibration module 3 (such as a ring-shaped ultrasonic generator) on the top of the grinding wheel ring 1. Ultrasonic vibration can promote the electrolyte to penetrate more evenly into the contact area between the grinding wheel and the workpiece, enhance the diffusion ability of the electrolyte, accelerate the dissolution and peeling process of the oxide film, and thus improve the removal efficiency of the oxide film. At the same time, this high-frequency vibration can also effectively reduce the cutting force and reduce the subsurface damage caused by the mechanical removal effect of the composite abrasive particles 221.

[0057] Thanks to the integration of the ultrasonic vibration module 3, the grinding wheel proposed in this solution can achieve the synergistic effect of electrochemical-ultrasonic-mechanical grinding. Under the action of electrochemical corrosion, the workpiece surface material is softened by the electrolyte and generates low-hardness oxides. Combined with the mechanical removal effect of the grinding wheel and the high-frequency vibration effect of the ultrasonic vibration module 3, the electrolyte diffusion efficiency and oxide film removal effect are significantly improved, thereby effectively reducing the formation of subsurface damage on the workpiece surface.

[0058] To further explain, the raw materials of the composite abrasive 221 include abrasive grains, ceramic binders and nanoparticles, and the abrasive grains and nanoparticles are embedded in the interior of an adhesive matrix formed by curing the ceramic binder;

[0059] The abrasive grains have a particle size of 100 to 20,000 mesh, and the volume of the abrasive grains is 10 to 40% of the volume of the composite abrasive grains 221. The abrasive grains include any one or more combinations of diamond, boron carbide, silicon carbide, alumina, chromium oxide and CeO2.

[0060] The volume of the ceramic binder is 50-85% of the volume of the composite abrasive 221, and the ceramic binder is a Bi2O3-B2O3 ceramic binder.

[0061] The mass of the nanoparticles is 5-10% of the mass of the ceramic binder, and the nanoparticles are nano-SiC particles or nano-ZrO2 particles.

[0062] In a preferred embodiment of this technical document, the composite abrasive 221 is essentially a composite structure in which abrasive grains and nanoparticles are embedded in a bonding matrix formed by a ceramic binder. This composition utilizes the high hardness and wear resistance of diamond and CeO2 abrasive grains, while the Bi2O3-B2O3 component in the ceramic binder provides excellent thermal shock resistance and chemical stability. Furthermore, the ceramic binder in this system can effectively reduce the sintering temperature to 560°C, thereby avoiding damage to the diamond abrasive caused by high temperatures. In addition, to further improve the bending strength of the grinding wheel, 5-10 wt% of nanoparticles are added to enhance the overall mechanical properties of the grinding wheel, enabling it to remain stable under high-intensity processing conditions. At the same time, the catalytic effect of the nanoparticles can accelerate the electrochemical reaction process.

[0063] To simultaneously consider the various properties of the composite abrasive 221, this scheme also limits the proportions of each raw material. Specifically, an excessively high proportion of abrasive particles may reduce the fixing effect of the ceramic binder on the abrasive particles, causing premature detachment, while a low proportion may lead to a decrease in the removal rate. Therefore, the volume of the abrasive particles is limited to 10-40% of the volume of the composite abrasive 221. The addition of 5-10 wt% nanoparticles can improve mechanical properties without excessively altering the sintering properties of the ceramic binder; however, an excessively high nanoparticle content may lead to agglomeration, which would reduce the reinforcing effect.

[0064] To further clarify, the active metal 222 is a bismuth alloy or a copper alloy, and the conductive binder 224 is a copper or titanium alloy.

[0065] Taking into account the electrochemical nanogrinding process, this scheme optimizes the specific materials of active metal 222 and conductive binder 224 based on their electrical conductivity, thermal conductivity, corrosion resistance, strength, hardness, and cost.

[0066] Furthermore, the porosity of the core 21 is 20-30%;

[0067] The core 21 includes a porous inner layer and a porous outer wall that wraps around the porous inner layer.

[0068] The pore size distribution of the porous inner layer is as follows: large pores account for 60-80% of the pore size structure volume, and medium pores account for 20-40% of the pore size structure volume.

[0069] The porous outer wall pore size distribution is as follows: medium pores account for 50-70% of the pore size structure volume, and large pores account for 30-50% of the pore size structure volume;

[0070] The mesopores have a particle size of 10–50 nm, and the macropores have a pore size of 100–300 micrometers.

[0071] To further ensure the continuity and efficiency of the processing, this solution also adopts gradient pore technology to set a pore structure with gradient design inside the core 21, which is conducive to rapid transport in the porous inner layer and increases the surface area in the porous outer wall, taking into account both mass transfer and reactivity.

[0072] In one specific embodiment, the core 21 is composed of nano-SiC and walnut shell powder. Due to its natural porous nature, walnut shell powder effectively promotes electrolyte penetration; this porous structure helps the electrolyte quickly penetrate into the grinding wheel, while also allowing for the timely removal of reaction products generated during processing, preventing clogging. Nano-SiC provides additional mechanical support, ensuring the stability of the porous structure. Furthermore, the high hardness and wear resistance of nano-SiC ensure the stability of the porous structure during high-intensity processing, extending the service life of the grinding wheel.

[0073] Furthermore, the grinding wheel block 2 also includes an anti-passivation layer 23, and the anti-passivation layer 23 is wrapped around the outside of the outer layer 22;

[0074] The passivation-resistant layer 23 is a tantalum carbide layer or a graphene layer.

[0075] To prevent the grinding wheel from being corroded by the electrolyte during processing, this solution also uses an anti-passivation coating technology to treat the side of the grinding wheel. The grinding wheel surface is covered with a tantalum carbide layer or a graphene layer, which effectively reduces the corrosion of the grinding wheel substrate by the electrolyte and extends its service life.

[0076] It should be noted that either the tantalum carbide layer or the graphene layer can be applied to the outside of the outer layer 22 using existing chemical vapor deposition techniques, which will not be elaborated on here.

[0077] A silicon carbide electrochemical nanogrinding method, using an upper grinding wheel, includes the following steps:

[0078] A. Fix the grinding wheel 100 to the polishing spindle, and fix the silicon carbide wafer 200 to be processed to the workpiece table; then, connect the negative terminal of the pulse power supply to the grinding wheel 100, and connect the positive terminal of the pulse power supply to the silicon carbide wafer 200.

[0079] The electrolyte circulation system 300 continuously supplies electrolyte to the processing surface of the silicon carbide wafer, and the processing surface of the silicon carbide wafer is completely immersed in the electrolyte.

[0080] B. Start the pulse power supply, the polishing spindle, the workpiece worktable and the ultrasonic vibration module 3, and make the grinding wheel 100 and the silicon carbide wafer 200 rotate relative to each other through the polishing spindle and the workpiece worktable;

[0081] C. The grinding wheel 100 feeds into the silicon carbide wafer 200, and the grinding wheel 100 performs electrochemical nano-grinding on the processing surface of the silicon carbide wafer 200.

[0082] Single-crystal silicon carbide (SiC) wafers, as the core substrate of third-generation semiconductor materials, possess high thermal conductivity, high breakdown field strength, and excellent chemical stability, and are widely used in high-voltage, high-frequency, and high-temperature electronic devices. However, their extremely high hardness and brittleness (Mohs hardness 9.2-9.5) lead to problems such as rapid wheel wear, low processing efficiency, and severe subsurface damage in traditional machining methods, especially in the processing of large-size (e.g., 8-inch) wafers.

[0083] Therefore, this solution also proposes a silicon carbide electrochemical nanogrinding method using the aforementioned grinding wheel, as shown in the schematic diagram below. Figure 2 As shown, this method can significantly improve the efficiency of achieving a quasi-smooth surface on silicon carbide wafers while reducing the processing cost of silicon carbide. It should be noted that the electrochemical nanogrinding method described in this scheme can be implemented using existing electrochemical nanogrinding equipment; the specific structure of the equipment will not be described in detail here.

[0084] Thanks to the composite structure design of the grinding wheel in this scheme, the electrochemical nanogrinding method proposed in this scheme can achieve an organic combination of the two stages of electrochemical activity and mechanical removal, realizing efficient and high-quality processing of high-hardness silicon carbide materials.

[0085] Specifically, in the electrochemical activation stage: the grinding wheel 100 serves as the cathode, and the workpiece (silicon carbide wafer 200) serves as the anode. Under the action of an electric field, the electrolyte forms a softened oxide layer (SiO2) on the surface of the silicon carbide wafer 200. This process is one of the core steps of the entire process, and its main purpose is to form an easily removable softened oxide layer on the surface of the workpiece through an electrochemical reaction.

[0086] Mechanical removal stage: The abrasive grains of the grinding wheel 100 directly remove the softened oxide layer generated during the electrochemical activation stage through mechanical action. The key to this stage lies in the effective contact and force transmission between the abrasive grains of the grinding wheel 100 and the workpiece surface. To further enhance the material removal effect, ultrasonic vibration-assisted technology is employed. Ultrasonic vibration significantly enhances the peeling ability of the grinding wheel abrasive grains against brittle reaction products through high-frequency oscillation, reduces cutting force, and minimizes subsurface damage. This technical solution, combining mechanical action and ultrasonic vibration, not only improves the material removal rate but also ensures the smoothness and consistency of the machined surface.

[0087] To further clarify, in step A, the electrolyte includes any one or more combinations of NaOH, NaCl, KaCl, KNO3, ethylene carbonate, and propylene carbonate solutions, and the concentration of the electrolyte is 5-15%.

[0088] In step B, the voltage of the pulse power supply is 5-20V and the frequency is 1-10kHz.

[0089] In a preferred embodiment of this technical solution, optimizing the relevant process parameters of the electrochemical activation stage is beneficial for achieving efficient and high-quality material removal. Specifically:

[0090] To further precisely control the oxide film formation rate, pulse power supply technology was introduced, with its frequency set in the range of 1 to 10 kHz; at the same time, the voltage range was set to 5 to 20 V, which can effectively balance the oxide film formation rate and the workpiece surface quality.

[0091] The choice of electrolyte has a certain impact on the efficiency of electrochemical reaction. Therefore, NaOH or KNO3 solution was used as the main medium, and its concentration was controlled at 5-15%. This concentration range can ensure the conductivity of the electrolyte and avoid the increase of side reactions due to excessive concentration.

[0092] To further explain, in step B, the polishing spindle is started and the linear velocity of the grinding wheel 100 is set to 10-20 m / s; the workpiece stage is started and the rotational speed of the silicon carbide wafer 200 is set to 2-5 m / s; the amplitude of the ultrasonic vibration module 3 is 5-20 μm.

[0093] In step C, the feed speed of the grinding wheel 100 is 0.05 to 0.2 μm / s.

[0094] In a preferred embodiment of this technical solution, optimizing the relevant process parameters of the mechanical removal stage is beneficial for achieving efficient material removal while maintaining the integrity of the workpiece surface. Specifically:

[0095] The linear velocity of the grinding wheel 100 is set within the range of 10–20 m / s. This speed range ensures sufficient contact between the abrasive grains of the grinding wheel 100 and the workpiece surface, while avoiding heat accumulation problems caused by excessive linear velocity. The rotational speed of the silicon carbide wafer 200 is controlled between 2 and 5 m / s to ensure uniform force distribution on all parts of the workpiece surface and avoid localized excessive wear or uneven processing.

[0096] In addition, by setting the ultrasonic amplitude in the range of 5 to 20 μm, it is possible to effectively assist in the peeling of brittle reaction products, reduce cutting force and reduce subsurface damage.

[0097] In step C, the feed speed of the grinding wheel 100 is controlled between 0.05 and 0.2 μm / s, which is the distance that the grinding wheel 100 approaches the silicon carbide wafer 200 per unit time. The feed speed controls the material removal rate and surface quality. This range can minimize surface roughness while ensuring efficient material removal.

[0098] To further clarify, in step C, the processing temperature of the electrochemical nano-grinding is <50℃.

[0099] Temperature control is another crucial aspect for preventing thermal damage, extending grinding wheel life, and ensuring machining stability. This solution limits the machining temperature of electrochemical nanogrinding to <50℃. The low-temperature environment not only effectively avoids workpiece deformation or thermal damage caused by high temperatures but also significantly improves the durability of the grinding wheel and machining efficiency. Furthermore, it helps maintain the stability of the electrolyte, thereby further optimizing the electrochemical reaction conditions.

[0100] It should be noted that this solution can maintain the processing temperature of electrochemical nanogrinding at an ideal temperature by setting a cooling system outside the workpiece stage (such as attaching the cooling end of a semiconductor cooler to the polishing pad); or by cooling the recovered electrolyte and then spraying it back onto the processing area to reduce the processing temperature of electrochemical nanogrinding. This solution is not limited to these specific methods.

[0101] To elaborate further, step C also includes:

[0102] The processing voltage, current and / or grinding force during the electrochemical nano-grinding process are monitored in real time, and the concentration of the electrolyte and the output parameters of the pulse power supply, the polishing spindle, the workpiece table and / or the ultrasonic vibration module 3 are dynamically adjusted.

[0103] As an improvement on the aforementioned electrochemical nanogrinding method, this scheme further incorporates a real-time control stage in step C. By monitoring the processing voltage, current, and / or grinding force during the electrochemical nanogrinding process in real time, the concentration of the electrolyte and the output parameters of the pulse power supply, polishing spindle, workpiece table, and / or ultrasonic vibration module 3 are dynamically adjusted to achieve cyclic optimization of the "softening-removal" process. This closed-loop control not only improves processing accuracy but also significantly extends the service life of the grinding wheel, while avoiding workpiece damage or decreased processing efficiency due to improper parameter settings. Furthermore, it can promptly detect and correct abnormalities in the electrochemical reaction, ensuring the stability of the processing.

[0104] Specifically, this solution can perform real-time monitoring through any one or more of the following methods:

[0105] (1) Connect the positive and negative terminals of the voltage sensor (such as a differential probe) to the grinding wheel electrode and the workpiece electrode respectively. This can be used to measure the potential difference between the grinding wheel and the workpiece and to monitor the processing voltage in real time during the electrochemical nanogrinding process.

[0106] (2) Connecting the current sensor in series into the current circuit of electrolytic machining can be used to measure the current flowing through the circuit and monitor the current in real time during the electrochemical nano-grinding process.

[0107] (3) The force sensor is installed on the grinding wheel spindle or feed mechanism, or embedded inside the grinding wheel 100, and can be used to sense the force generated during the grinding process and monitor the grinding force in real time during the electrochemical nanogrinding process.

[0108] Example

[0109] A. Fix the grinding wheel 100 to the polishing spindle, and at the same time fix the silicon carbide wafer 200 to be processed to the workpiece table; then, connect the negative terminal of the pulse power supply to the grinding wheel 100, and at the same time connect the positive terminal of the pulse power supply to the silicon carbide wafer 200.

[0110] The electrolyte circulation system 300 continuously delivers a 10% KNO3 solution to the processing surface of the silicon carbide wafer, and the processing surface of the silicon carbide wafer is completely immersed in the KNO3 solution.

[0111] The grinding wheel 100 includes a grinding wheel ring 1, a grinding wheel block 2, and an ultrasonic vibration module 3. The grinding wheel ring 1 is a conductive copper ring. Multiple grinding wheel blocks 2 are provided and are spaced apart at the bottom of the grinding wheel ring 1. The ultrasonic vibration module 3 is installed on the top of the grinding wheel ring 1, and the radiating end of the ultrasonic vibration module 3 faces the top of the grinding wheel ring 1.

[0112] The grinding wheel block 2 includes a core 21 and an outer layer 22 wrapped around the core 21. The core 21 has a porous structure with a porosity of 20%. The outer layer 22 is essentially a composite structure of composite abrasive grains 221, Cu-Ni alloy and carbon fiber 223 embedded in a conductive substrate solidified by copper. The composite abrasive grains 221 are essentially a composite structure of diamond abrasive grains, CeO2 abrasive grains and nano ZrO2 particles embedded in a bonding substrate solidified by Bi2O3-B2O3 ceramic binder.

[0113] B. Start the pulse power supply, with a voltage of 10V and a frequency of 5kHz.

[0114] Start the polishing spindle to make the linear speed of the grinding wheel 100 15 m / s; start the workpiece table to make the rotation speed of the silicon carbide wafer 200 3 m / s, and make the grinding wheel 100 and the silicon carbide wafer 200 rotate relative to each other.

[0115] Start the ultrasonic vibration module 3, and set the amplitude of the ultrasonic vibration module 3 to 10 μm.

[0116] C. Feed the grinding wheel 100 to the silicon carbide wafer 200 at a feed speed of 0.1 μm / s, and perform electrochemical nano-grinding on the processing surface of the silicon carbide wafer 200 by the grinding wheel 100 (maintain the processing temperature <50℃ during the processing) until the processing surface of the silicon carbide wafer 200 reaches a laser-transparent quasi-smooth surface (Ra≤2nm).

[0117] Comparative Example

[0118] A. Fix the grinding wheel made of a single pure copper binder to the polishing spindle, and fix the silicon carbide wafer 200 to be processed to the workpiece table; then, connect the negative terminal of the pulse power supply to the grinding wheel 100, and connect the positive terminal of the pulse power supply to the silicon carbide wafer 200.

[0119] The electrolyte circulation system 300 continuously delivers a 10% KNO3 solution to the processing surface of the silicon carbide wafer, and the processing surface of the silicon carbide wafer is completely immersed in the KNO3 solution.

[0120] The aforementioned grinding wheel is essentially a structure in which diamond abrasive grains are embedded in a conductive substrate made of copper.

[0121] B. Start the pulse power supply, with a voltage of 10V and a frequency of 5kHz.

[0122] Start the polishing spindle to make the linear speed of the grinding wheel 15m / s; start the workpiece table to make the rotation speed of the silicon carbide wafer 200 3m / s, and make the grinding wheel and the silicon carbide wafer 200 rotate relative to each other.

[0123] C. Feed the grinding wheel to the silicon carbide wafer 200 at a feed speed of 0.1 μm / s, and perform electrochemical nano-grinding on the processing surface of the silicon carbide wafer 200 by the grinding wheel 100 (maintain the processing temperature <50℃ during the processing) until the processing surface of the silicon carbide wafer 200 reaches a laser-transparent quasi-smooth surface (Ra≤2nm).

[0124] The processing results of the above embodiments and comparative examples show that the grinding wheel of this scheme is simple to prepare and low in cost. Under the action of electrochemical catalysis, it can effectively corrode the surface of silicon carbide wafers and form a soft layer that is easier to remove. At the same time, under the action of ultrasonic assistance, it is easier to remove the material on the surface of silicon carbide wafers, which improves grinding efficiency and greatly reduces grinding force, further reducing processing costs.

[0125] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A grinding wheel, characterized in that: It includes a grinding wheel ring, grinding wheel blocks, and an ultrasonic vibration module; the grinding wheel ring is a conductive ring, multiple grinding wheel blocks are provided, and the multiple grinding wheel blocks are spaced apart at the bottom of the grinding wheel ring, and the ultrasonic vibration module is installed on the top of the grinding wheel ring, with the radiating end of the ultrasonic vibration module facing the top of the grinding wheel ring; The grinding wheel block includes a core and an outer layer that wraps around the core; The core has a porous structure; The outer layer comprises composite abrasive particles, active metal, carbon fiber, and conductive binder, and the composite abrasive particles, active metal, and carbon fiber are embedded in the interior of a conductive matrix formed by curing the conductive binder. The raw materials for the composite abrasive include abrasive grains, ceramic binders, and nanoparticles, and the abrasive grains and nanoparticles are embedded in the interior of an adhesive matrix formed by curing the ceramic binder. The abrasive grains have a particle size of 100 to 20,000 mesh, and the volume of the abrasive grains is 10 to 40% of the volume of the composite abrasive grains. The abrasive grains include any one or more combinations of diamond, boron carbide, silicon carbide, alumina, chromium oxide, and CeO2. The volume of the ceramic binder is 50-85% of the volume of the composite abrasive, and the ceramic binder is a Bi2O3-B2O3 ceramic binder. The mass of the nanoparticles is 5-10% of the mass of the ceramic binder, and the nanoparticles are nano-SiC particles or nano-ZrO2 particles. The porosity of the core is 20-30%; The core includes a porous inner layer and a porous outer wall that wraps around the porous inner layer. The pore size distribution of the porous inner layer is as follows: large pores account for 60-80% of the pore size structure volume, and medium pores account for 20-40% of the pore size structure volume. The porous outer wall pore size distribution is as follows: medium pores account for 50-70% of the pore size structure volume, and large pores account for 30-50% of the pore size structure volume; The mesopores have a particle size of 10–50 nm, and the macropores have a pore size of 100–300 μm.

2. A grinding wheel according to claim 1, characterized in that: The active metal is a bismuth alloy or a copper alloy, and the conductive binder is a copper or titanium alloy.

3. A grinding wheel according to claim 1, characterized in that: The grinding wheel block also includes an anti-passivation layer, and the anti-passivation layer is wrapped around the outside of the outer layer; The passivation-resistant layer is a tantalum carbide layer or a graphene layer.

4. A silicon carbide electrochemical nanogrinding method, characterized in that, Using the grinding wheel according to any one of claims 1 to 3, the process includes the following steps: A. Fix the grinding wheel to the polishing spindle, and fix the silicon carbide wafer to be processed to the workpiece table; then, connect the negative terminal of the pulse power supply to the grinding wheel, and connect the positive terminal of the pulse power supply to the silicon carbide wafer. The electrolyte is continuously supplied to the processing surface of the silicon carbide wafer through an electrolyte circulation system, and the processing surface of the silicon carbide wafer is completely immersed in the electrolyte. B. Start the pulse power supply, the polishing spindle, the workpiece table and the ultrasonic vibration module, and make the grinding wheel and the silicon carbide wafer rotate relative to each other through the polishing spindle and the workpiece table; C. The grinding wheel is fed to the silicon carbide wafer, and the grinding wheel performs electrochemical nano-grinding on the processing surface of the silicon carbide wafer.

5. The silicon carbide electrochemical nanogrinding method according to claim 4, characterized in that, In step A, the electrolyte comprises any one or more combinations of NaOH, NaCl, KaCl, KNO3, ethylene carbonate, and propylene carbonate solutions, and the concentration of the electrolyte is 5-15%. In step B, the voltage of the pulse power supply is 5-20V and the frequency is 1-10kHz.

6. The silicon carbide electrochemical nanogrinding method according to claim 4, characterized in that, In step B, the polishing spindle is started and the linear speed of the grinding wheel is set to 10-20 m / s; Start the workpiece stage and rotate the silicon carbide wafer at a speed of 2-5 m / s; the amplitude of the ultrasonic vibration module is 5-20 μm. In step C, the feed speed of the grinding wheel is 0.05 to 0.2 μm / s.

7. The silicon carbide electrochemical nanogrinding method according to claim 4, characterized in that, In step C, the processing temperature of the electrochemical nano-grinding is <50℃.

8. The silicon carbide electrochemical nanogrinding method according to claim 4, characterized in that, Step C also includes: The processing voltage, current, and / or grinding force during the electrochemical nanogrinding process are monitored in real time, and the concentration of the electrolyte and the output parameters of the pulse power supply, the polishing spindle, the workpiece table, and / or the ultrasonic vibration module are dynamically adjusted.

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