High self-sharpening diamond grinding wheel and preparation method thereof

Abstract

The present application relates to a kind of high self-sharpening diamond grinding wheel, the grinding wheel is made of the following weight percentage raw materials: diamond abrasive 25-50%, silicon carbide abrasive 10-30%, hybrid modified fiber 0.5-5%, chromium oxide powder 1-10%, chromium aluminum carbide powder 0.5-5%, illite powder 1-10% and blending modified resin powder 30-60%. Under the same conditions, the present application grinding wheel is polished IGBT module experimental block, and the smoothness Ra is not more than 0.5 μm, can be durable 6.5h above, and the grinding effect is obviously superior to existing grinding wheel.

Description

A high self-sharpening diamond grinding wheel and its preparation method Technical Field

[0001] This invention belongs to the field of organic abrasive manufacturing technology, and relates to a high self-sharpening diamond grinding wheel, its preparation method, and its application. Specifically, this grinding wheel can be used for precision grinding of discontinuous structures of hard and soft phases, such as the grinding of IGBT modules. Background Technology

[0002] An Insulated Gate Bipolar Transistor (IGBT) is a new type of power semiconductor device with metal-oxide-semiconductor input and bipolar output functions, commonly known as the "CPU" of power electronic devices. IGBT module packaging materials include a DBC substrate (mainly composed of ceramics such as alumina, aluminum nitride, and silicon nitride covered with oxygen-free copper), a heat sink (pure copper, Al / SiC metal-based composite materials, and graphene / copper composite materials), potting materials (epoxy resin, silicone, polyimide, and other polymer materials), and an outer casing material (resins, ceramics, and metals are all used, with epoxy resin being the most widely used).

[0003] Grinding is a post-packaging process for IGBT modules, primarily involving grinding the heat sink base plates and the outer casing encapsulation material on both sides. The grinding removal amount is 0.1-1mm. The heat sink base plates and outer casing encapsulation materials include easily burned resin materials, hard inorganic fillers, and soft metal materials that easily adhere to the material surface. The material properties vary widely, making grinding difficult. Currently available domestically produced grinding wheels have drawbacks such as being unable to grind effectively, being easily burned, and having low durability, failing to meet usage requirements. At present, domestic research institutions and related manufacturers have not yet conducted research or reported on corresponding grinding wheels, and the grinding wheels used are heavily reliant on imports. Summary of the Invention

[0004] To meet the grinding requirements of semiconductor devices and modules such as IGBTs, and to adapt to high-efficiency, high-quality, and long-life grinding processes for discontinuous structures of hard and soft phases, structures with low thermal conductivity and easy burning, and structures with large machining volume and high machining rate, this invention provides a high self-sharpening diamond grinding wheel and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A high self-sharpening diamond grinding wheel is made from the following raw materials in weight percentages: 25-50% diamond abrasive, 10-30% silicon carbide abrasive, 0.5-5% mixed modified fiber, 1-10% chromium oxide powder, 0.5-5% chromium aluminum carbide powder (Cr2AlC), 1-10% illite powder, and 30-60% blended modified resin powder.

[0007] Specifically, the hybrid modified fiber is composed of 20-30% carbon nanotubes and 70-80% aramid fibers. Carbon nanotubes have good rigidity but are brittle, while aramid fibers have weak reinforcing effect but good flexibility. The addition of these two fibers can improve the impact resistance and bending strength of the grinding wheel and reduce its wear ratio. Before use, the hybrid fibers are mixed evenly, impregnated with a silane coupling agent, stirred evenly, dried, and ground for later use. The surface-modified fibers have a tight bridge with the resin binder, resulting in a significant reinforcing effect. Further, the hybrid modified fiber is obtained through the following treatment: the hybrid fiber composed of carbon nanotubes and aramid fibers is impregnated with a 0.5-20% silane coupling agent solution, stirred evenly, then dried at 80-120℃ and ground to obtain the final product; the silane coupling agent used is A-151, KH550, KH590, or B202, etc., and the solvent can be alcohols or water, such as methanol or ethanol.

[0008] Specifically, the blended modified resin is composed of 10-30% melamine-formaldehyde resin (MF) and 70-90% phenolic resin (PF), and can be prepared by an organic solvent dissolution-spray-drying-dispersion method. Further, the blended modified resin powder is obtained through the following treatment: melamine-formaldehyde resin and phenolic resin are dissolved in an organic solvent (such as n-butanol or N,N-dimethylformamide DMF, etc.), spray-dried, and then dispersed to obtain the final product. Melamine-formaldehyde resin has good wear resistance, fast curing speed, a curing temperature close to that of phenolic resin, and stable chemical properties. Blending it with phenolic resin increases the brittleness and self-sharpening properties of the resin binder, preventing grinding wheel clogging and achieving the purpose of unblocking.

[0009] The aforementioned high self-sharpening diamond grinding wheel contains diamond abrasive with a particle size of 1-600 micrometers, silicon carbide abrasive with a particle size of 1-300 micrometers, chromium oxide powder with a particle size of 0.3-50 micrometers, chromium aluminum carbide powder with a particle size of 1-100 micrometers, and illite powder with a particle size of 1-30 micrometers. The carbon nanotubes have a diameter of 10-300 nm and an aspect ratio of 10-1000; the aramid fibers have a diameter of 1-50 micrometers and an aspect ratio of 10-1000.

[0010] In the grinding wheel formulation of this invention, chromium aluminum carbide powder is a lamellar lubricant. Compared to traditional graphite lubricants, lamellar chromium aluminum carbide exhibits excellent self-lubricating properties at both high and low temperatures. At high temperatures, Cr2O3, formed by the oxidation of Cr in Cr2AlC, is also an excellent self-lubricating material. Simultaneously, the generated Al2O3 possesses strong stability and oxidation resistance, resulting in high-temperature self-lubricating ability, significantly reducing the friction coefficient of the grinding wheel and preventing grinding burns. Illite powder is a lamellar modified filler. Lamellar illite has a Mohs hardness of only about 1 and is brittle; its addition reduces the hardness and strength of the binder system, further increasing its self-sharpening properties.

[0011] This invention provides a method for preparing the above-mentioned high self-sharpening diamond grinding wheel, which includes the following steps:

[0012] 1) Add silicon carbide abrasive, chromium oxide powder, chromium aluminum carbide powder and illite powder to a V-type mixer in proportion, dry mix evenly, and set aside for use;

[0013] 2) Wet the diamond abrasive evenly with a wetting agent, add the blended modified resin, mix well, sieve, and set aside for use;

[0014] 3) Mix the hybrid modified fiber with the materials obtained in steps 1) and 2) evenly, add grinding balls and anhydrous alcohol that covers the total material, ball mill, dry, and sieve to obtain the molding material;

[0015] 4) Place the molding material into the assembled mold with the base, level the material, and cover it with the pressure head; place the mold on a hot press at 150-220℃, preheat and apply pressure, hold at 1-3 MPa for 20-50 minutes, cool to 80-110℃ to release pressure and demold, obtaining the grinding wheel. Process it according to conventional methods in this field. The prepared grinding wheel has good self-sharpening properties, low grinding temperature, and strong impact resistance. It is suitable for ordinary wet grinding, ultrasonic vibration-assisted grinding, and other grinding methods, and the grinding parameters have a wide adjustable range.

[0016] Specifically, in step 3), the ball milling process is carried out for 1-10 hours with a ball-to-material ratio of 5-20:1, followed by drying at 80-150℃.

[0017] The innovation and key points of this invention are as follows: The addition of blended modified resin and brittle illite filler improves the self-sharpening and unblocking properties of the binder. The addition of novel lamellar chromium aluminum carbide powder (Cr2AlC) reduces grinding resistance and controls the temperature in the grinding zone. The addition of hybrid modified fibers enhances the impact resistance of the grinding wheel and reduces its wear ratio. Through a rational powder mixing and modification process design, utilizing various methods such as impregnation, dry mixing, spray drying, and ball milling, the uniformity and formability of the mixture are improved, ensuring compatibility with existing molding and processing technologies, resulting in a grinding wheel with excellent overall performance. It can be applied to grinding in fields such as IGBT modules, meeting the high-efficiency, high-quality, and long-life grinding requirements for discontinuous structures of hard and soft phases, low thermal conductivity structures prone to burns, and structures with large machining volumes and high machining rates. This is a first in the domestic industry.

[0018] To address the problems of existing products and technologies, such as poor self-sharpening properties, easy burning of workpieces, and low machining accuracy, this invention has the following beneficial effects:

[0019] 1) This invention develops a copper-repellent high self-sharpening binder by adding blended modified resin and brittle illite filler, thereby improving the self-sharpening property of the grinding wheel and solving the problem of poor chip tolerance;

[0020] 2) This invention reduces grinding resistance and controls the temperature in the grinding zone by adding a novel lamellar chromium aluminum carbide powder (Cr2AlC), thus solving the problem of burns;

[0021] 3) This invention improves the impact resistance of the grinding wheel and reduces its wear ratio by adding hybrid modified fibers, thus solving the problem of low machining accuracy of the grinding wheel;

[0022] 4) This invention designs reasonable mixing and modification processes for different raw materials. Through various methods such as impregnation, dry mixing, spray drying, and ball milling, the uniformity and formability of the mixture are improved. It is compatible with existing molding and processing technologies, and the grinding wheel has excellent comprehensive performance and wide applicability.

[0023] Through the development and innovation of the aforementioned key technologies, the grinding wheel of this invention can meet the high-efficiency, high-quality, and long-life grinding requirements of IGBT modules and other fields, particularly for discontinuous structures with hard and soft phases, structures prone to burning due to low thermal conductivity, and structures requiring large machining volumes and high machining rates. Under the same conditions, when grinding IGBT module test blocks, the surface finish Ra of the grinding wheel of this invention does not exceed 0.5 μm, and it can withstand more than 6.5 hours of grinding, demonstrating significantly better grinding performance than existing grinding wheels. Attached Figure Description

[0024] Figure 1 is a schematic diagram of the 1A1 type grinding wheel;

[0025] Figure 2 is a schematic diagram of the 6A2 type grinding wheel. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] In the following examples, unless otherwise specified, all raw materials used are commercially available products that can be directly purchased or prepared using conventional methods in the art. Unless otherwise specified, all processes used employ conventional techniques in the art, such as spray drying. Example 1

[0028] A high self-sharpening diamond grinding wheel is made of raw diamond abrasive, silicon carbide abrasive, hybrid modified fiber (composed of carbon nanotubes and aramid fibers), chromium oxide powder, chromium aluminum carbide powder, illite powder, and blended modified resin powder (composed of melamine-formaldehyde resin and phenolic resin). The specific weight ratio of each raw material is shown in the table below.

[0029]

[0030] The preparation method of the above-mentioned high self-sharpening diamond grinding wheel specifically includes the following steps:

[0031] 1) Immerse the mixed fibers (carbon nanotubes and aramid fibers) in 1% KH550 ethanol solution (the amount should be enough to submerge the fibers), stir evenly (about 5 minutes), then dry at 100℃ for 1 hour, grind and disperse, and set aside for use;

[0032] 2) Add silicon carbide, chromium oxide, chromium aluminum carbide and illite to a V-type mixer and mix evenly. Set aside for later use.

[0033] 3) Melamine-formaldehyde resin and phenolic resin were dissolved in n-butanol and a blended resin was prepared by spray drying (drying temperature about 110℃). The mixture was then ground and set aside for use.

[0034] 4) Wet the diamond abrasive with commercially available analytical grade cresol as a wetting agent until uniform, add the blended modified resin from step 3), mix well, sieve, and set aside for use;

[0035] 5) Mix the materials from steps 1), 2), and 4) evenly, add grinding balls and anhydrous ethanol to cover the total material, and ball mill for 5 hours, with a ball-to-material ratio of 5:1. Then dry at 100℃ and sieve (through an 80-mesh standard sieve). The mixing is now complete.

[0036] 6) Pour the molding material into the assembled 1A1 grinding wheel mold with the substrate, level the material, and cover it with the pressure head; place the mold on a hot press at 160°C, preheat and pressurize, hold the pressure at 1.5 MPa for 50 minutes, cool to 80°C, release the pressure and demold to obtain the grinding wheel, and process it according to conventional methods in the art. The structural schematic diagram is shown in Figure 1. Example 2

[0037] A high self-sharpening diamond grinding wheel is made of raw diamond abrasive, silicon carbide abrasive, hybrid modified fiber (composed of carbon nanotubes and aramid fibers), chromium oxide powder, chromium aluminum carbide powder, illite powder, and blended modified resin powder (composed of melamine-formaldehyde resin and phenolic resin). The specific weight ratio of each raw material is shown in the table below.

[0038]

[0039] The preparation method of the above-mentioned high self-sharpening diamond grinding wheel specifically includes the following steps:

[0040] 1) Immerse the mixed fibers (carbon nanotubes and aramid fibers) in a 2.5% KH590 ethanol solution (enough to submerge the fibers), stir evenly (about 5 minutes), then dry at 100°C for 1 hour, grind and disperse, and set aside for use;

[0041] 2) Add silicon carbide, chromium oxide, chromium aluminum carbide and illite to a V-type mixer and mix evenly. Set aside for later use.

[0042] 3) Melamine-formaldehyde resin and phenolic resin were dissolved in N,N-dimethylformamide and a blended resin was prepared by spray drying (drying temperature about 130℃). The mixture was then ground and set aside for use.

[0043] 4) Wet the diamond abrasive evenly with commercially available liquid paraffin as a wetting agent, add the blended modified resin from step 3), mix well, sieve, and set aside for use;

[0044] 5) Mix the materials from steps 1), 2), and 4) evenly, add grinding balls and anhydrous ethanol to cover the total material, and ball mill for 6 hours, with a ball-to-material ratio of 6:1. Then dry at 100℃ and sieve (through a 50-mesh standard sieve). The mixing is now complete.

[0045] 6) Put the molding material into the assembled 6A2 grinding wheel mold with the base, scrape the material, and cover the pressure head; place the mold on a hot press at 165°C, preheat and press, hold pressure at 2 MPa for 50 minutes, cool down to 85°C to release pressure and demold, and obtain the grinding wheel. Process it according to conventional methods in this field to obtain the desired result. See Figure 2 for a schematic diagram of the structure.

[0046] Grinding effect test

[0047] The grinding wheels of Embodiments 1 and 2 of this invention were used to grind and verify the IGBT module test block. The grinding results were compared with those of commercially available grinding wheels of the same grit size, namely, commercially available product 1 and commercially available product 2. The results are shown in the table below.

[0048]

[0049] As shown in the table above, under the same conditions, when grinding IGBT module test blocks, the surface finish Ra of the grinding wheel of the present invention does not exceed 0.5μm and can last for more than 6.5 hours. The grinding effect is significantly better than that of existing grinding wheels.

Claims

1. A high self-sharpening diamond grinding wheel, characterized in that, The grinding wheel is made from the following raw materials in weight percentages: 25-50% diamond abrasive, 10-30% silicon carbide abrasive, 0.5-5% hybrid modified fiber, 1-10% chromium oxide powder, 0.5-5% chromium aluminum carbide powder, 1-10% illite powder, and 30-60% blended modified resin powder; the blended modified resin is composed of 10-30% melamine-formaldehyde resin and 70-90% phenolic resin; the hybrid modified fiber is obtained by the following treatment: the hybrid fiber composed of carbon nanotubes and aramid fibers is impregnated with a 0.5-20% silane coupling agent solution, stirred evenly, then dried at 80-120℃, and ground to obtain the final product; the silane coupling agent used is A-151, KH550, KH590, or B202.

2. The high self-sharpening diamond grinding wheel as described in claim 1, characterized in that, The hybrid modified fiber is composed of 20-30% carbon nanotubes and 70-80% aramid fibers.

3. The high self-sharpening diamond grinding wheel as described in claim 1, characterized in that, The blended modified resin powder is obtained by the following treatment: melamine-formaldehyde resin and phenolic resin are dissolved in an organic solvent, spray-dried, and then ground to obtain the powder.

4. The high self-sharpening diamond grinding wheel as described in claim 1, characterized in that, The diamond abrasive has a particle size of 1-600 micrometers, and the silicon carbide abrasive has a particle size of 1-300 micrometers.

5. The high self-sharpening diamond grinding wheel as described in claim 1, wherein the chromium oxide powder has a particle size of 0.3-50 micrometers, the chromium aluminum carbide powder has a particle size of 1-100 micrometers, and the illite powder has a particle size of 1-30 micrometers.

6. The high self-sharpening diamond grinding wheel as described in claim 1 or 2, characterized in that, The carbon nanotubes have a diameter of 10-300 nm and an aspect ratio of 10-1000; the aramid fibers have a diameter of 1-50 micrometers and an aspect ratio of 10-1000.

7. The method for preparing the high self-sharpening diamond grinding wheel according to any one of claims 1 to 6, characterized in that, The process includes the following steps: 1) Add silicon carbide abrasive, chromium oxide powder, chromium aluminum carbide powder and illite powder to a mixer in proportion, dry mix evenly, and set aside; 2) Wet diamond abrasive evenly with a wetting agent, add blended modified resin, mix evenly, sieve, and set aside; 3) Mix the blended modified fiber with the materials obtained in steps 1) and 2) evenly, ball mill, dry, and sieve to obtain a molding material; 4) Put the molding material into a mold with a pre-assembled substrate, scrape the material, and cover with a pressure head; place the mold on a hot press at 150-220℃, preheat, apply pressure, hold pressure at 1-3 MPa for 20-50 minutes, cool down to 80-110℃ to release pressure and demold, and obtain a grinding wheel, which is then processed according to conventional methods in the field.

8. The method for preparing a high self-sharpening diamond grinding wheel as described in claim 7, characterized in that, In step 3), the ball mill is performed for 1-10 hours with a ball-to-material ratio of 5-20:1, followed by drying at 80-150℃.

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