Grinding pad for rough polishing of CVD diamond and preparation method of grinding pad

Abstract

The invention belongs to the technical field of grinding tools, and relates to a grinding pad for CVD diamond rough polishing and a preparation method thereof.The grinding pad comprises a substrate and grinding blocks which are arranged on the substrate and provided with flat top faces, and the ratio of the diameter or the side length of each grinding block to the gap distance of the adjacent grinding blocks is (10-15): (1-1.5); the top of the grinding block is chamfered; the grinding block is prepared from the following raw materials: a diamond-silicon carbide grinding material, a binder, glass fibers and a filler; the roundness of the diamond-silicon carbide grinding material is 0.80-0.85, and the D50 particle size of the diamond-silicon carbide grinding material is 40-60 microns; the grinding pad has high strength and modulus, good stability and high grinding and polishing efficiency. The grinding blocks of the grinding pad are densely distributed, the grinding part is large, the grinding blocks are provided with chamfers and gaps, the CVD diamond can be prevented from being scratched in the polishing process, and chippings can be removed; the grinding material in the grinding pad is high in strength, good in self-sharpening performance and good in holding force, and therefore it can be guaranteed that the grinding pad has high grinding capacity in the rough polishing process, and the machining effect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of grinding tools, and in particular to a grinding pad and a preparation method thereof. Background Art

[0002] In recent years, driven by emerging industries such as electric vehicles and 5G communications, the third-generation semiconductor industry, mainly silicon carbide and gallium nitride, has received widespread attention and ushered in a period of rapid development. Diamond is the most promising candidate material for the next generation of power devices. Its bandgap (5.5 eV), thermal conductivity (2 000 W / m·K) and breakdown field strength (>10 MV / cm) are higher than those of silicon carbide, and it has stable chemical properties and strong radiation resistance. Diamond devices are mostly prepared by CVD method, among which polycrystalline CVD diamond film has high thermal conductivity and high surface flatness. Introducing it into the structure of semiconductor power devices can significantly improve the heat dissipation capacity of the device, so it has a broader application field and prospects. The processing of polycrystalline CVD diamond film materials is a complex process, among which ultra-precision polishing technology can reduce surface roughness and remove subsurface damage, playing a key role in diamond film processing. Due to the semiconductor industry's high requirements for crystal quality, coupled with the extremely high hardness and excellent chemical stability of diamond, which increases the difficulty of polishing, there is currently no complete processing route and fine polishing method that meets the requirements.

[0003] At present, the processing of polycrystalline CVD diamond mostly uses mechanical grinding, fluid abrasives and cast iron discs. This process can thin the polycrystalline CVD diamond substrate. This process belongs to three-body grinding. The particle size control requirements of the abrasive in three-body grinding are relatively strict. The appearance of individual larger particles is very likely to cause scratches and deep damage, and the roughness is high. The damage layer caused to the surface of the diamond after grinding is large. It is subsequently polished by a resin grinding wheel, and the polishing time can reach more than 20 hours. The grinding wheel can be polished because the grinding wheel has a high diamond content, many cutting edges, and a certain degree of elasticity. It can be used to reduce the roughness of polycrystalline CVD diamond, but it also has disadvantages. The resin diamond grinding wheel is expensive. Because the resin grinding wheel matrix has a certain degree of elasticity, the polishing cycle of polycrystalline CVD diamond is long and the efficiency is low. Therefore, it is necessary to develop a polishing product with a moderate matrix hardness that can be used to quickly reduce the roughness. Summary of the invention

[0004] In view of the technical problems of diamond polishing in the prior art, the present invention proposes a grinding pad for CVD diamond rough polishing and a preparation method thereof. The grinding pad has a special formula system, a high resin content, and extremely high toughness. The abrasive used in the system has high strength and special properties. The product can quickly remove the subsurface damage layer of the product, which is more efficient than simply relying on grinding wheel polishing. At the same time, the product has a simple manufacturing process, low cost, and low requirements on equipment, and a short polishing cycle, which improves production efficiency. It is suitable for large-scale production.

[0005] In order to achieve the above object, the technical solution of the present invention is achieved as follows: A grinding pad for CVD diamond rough polishing, comprising a base material and a plurality of grinding blocks with flat top surfaces arranged on the base material, wherein the ratio of the diameter or side length of the grinding blocks to the gap distance between adjacent grinding blocks is 10-15:1-1.5; the top of the grinding block is rounded; the raw materials for preparing the grinding block are: diamond-silicon carbide abrasive, a binder, glass fiber and filler.

[0006] Preferably, the top surface diameter or side length of the grinding block is 10-15 mm, and the gap is 1-1.5 mm; the fillet radius R of the top of the grinding block is 0.5-1 mm.

[0007] If the spacing ratio between the grinding blocks is too large, or the fillet radius R is too large, the contact area with the workpiece during processing will be small, affecting the surface processing quality. If the spacing ratio is too small or the fillet radius is too small, it will affect the demolding of the grinding particles and affect the chip removal during the grinding process.

[0008] Preferably, the ratio of the height of the grinding block (01) to the gap distance between adjacent grinding blocks (01) is 2-3:1; the roundness of the diamond-silicon carbide abrasive is 0.80-0.85, and the D50 particle size is 40-60 μm; and the binder is an epoxy resin polymer.

[0009] Preferably, the method for preparing the diamond-silicon carbide abrasive comprises the following steps: a) Diamond powder raw material with a Raman value of more than 3.0 is subjected to air flow crushing, shaping, sedimentation classification and other processes to obtain diamond powder with a D50 of about 40-60 μm, and a diamond-silicon carbide composite abrasive is prepared by the composite abrasive preparation method in patent CN118061074A, wherein the Raman value of the raw diamond used is more than 3.0; b) Mixing the obtained diamond-silicon carbide composite abrasive with diamond powders having a D50 of 10-30 μm and a D50 of 90-110 μm, and then putting the mixture into a steel barrel, wherein the volume of the diamond is less than one-half of the volume of the barrel, and adding a certain amount of steel balls into the barrel, and then mixing and stirring the mixture using a vertical three-dimensional mixer. After the mixing is completed, sieving the obtained mixture through 230# and 400# sieves to obtain diamond-silicon carbide abrasive powders having a circularity coefficient of 0.80-0.85 and a D50 range of 40-60 μm.

[0010] Preferably, the roundness of the diamond-silicon carbide composite abrasive in step (a) is greater than 0.7.

[0011] Preferably, in step (b), the mass ratio of the diamond-silicon carbide composite abrasive, the diamond powder with a D50 of 20 μm and the diamond powder with a D50 of 100 μm is 1:1:2-1:1:4.

[0012] Since the hardness of diamond-silicon carbide composite abrasive is slightly lower than that of diamond powder, it can be oriented and shaped with large and small diamond balls to achieve efficient shaping of its roundness. The diamond-silicon carbide composite abrasive obtained by this method has high roundness and particle size concentration. Different from the traditional ball milling process, the traditional ball milling process is to mix abrasives of various particle sizes together for ball milling shaping, which is less efficient. The surface of the diamond obtained by this ball milling method is rough. Due to the holding force of the resin matrix, the risk of abrasive falling off during processing is reduced.

[0013] The technical method of the present invention can be realized because the surface layer of the diamond-silicon carbide composite abrasive is basically silicon carbide, with a thickness of 2-3 μm and a strength slightly lower than that of pure diamond micropowder. Diamonds of different particle sizes can be used to efficiently shape the raw materials. At the same time, compared with single crystal diamond, the shaping of diamond-silicon carbide composite materials is easier, and the self-sharpening property of diamond-silicon carbide composite materials is better, which can ensure a stronger cutting force.

[0014] High-grade diamond micropowder with a Raman value of more than 3.0 is used because the grinding pad has higher grinding force and processing efficiency in the rough polishing process of polycrystalline CVD. The outer surface thickness of the diamond-silicon carbide composite abrasive can be controlled by the sintering process. The composite abrasive is mixed with diamond powder with D50≈20 and D50≈100μm in order to better screen out the abrasive with the target particle size after ball milling.

[0015] The above mass ratio is to ensure the shaping effect. The feeding amount and time of a single shaping are also for the shaping effect, to ensure that the composite abrasive with a roundness between 0.8-0.85 is obtained, to prevent the roundness from being too low, which will affect the polishing quality of the grinding pad, and the roundness from being too high, which will result in insufficient cutting force and affect the processing efficiency.

[0016] Preferably, the binder is bisphenol A epoxy resin, bisphenol S epoxy resin, bisphenol F epoxy resin or H epoxy resin; and the diameter of the glass fiber is 5-10 μm.

[0017] The binder has high strength and high modulus, which makes the overall hardness of the polishing pad higher and ensures the polishing ability. The glass fiber plays a role in enhancing the hardness and rigidity of the binder.

[0018] Preferably, the filler is one or any combination of calcium silicate, magnesium carbonate, sodium silicate and phosphate; the D50 particle size of the filler is 2-5 μm; Controlling the particle size of the filler within the above range can ensure the self-sharpening property of the grinding pad during the grinding process while ensuring the surface quality of the workpiece.

[0019] The base material (02) comprises an adhesive layer (03), a substrate layer (04) and a back adhesive layer (05); the adhesive layer (03) is formed by curing a silk screen after being impregnated with glue, wherein the glue is a mixture of epoxy thermosetting resin and inorganic powder; the substrate layer (04) is made of a PC board, a PET board or a PP board.

[0020] In order to facilitate the fixation of the grinding pad to the upper and lower discs of the grinding machine during use, the base material also includes a back glue layer, and the back glue layer is arranged on the side of the substrate layer away from the bonding layer.

[0021] Preferably, the mass fractions of the raw materials diamond-silicon carbide abrasive, binder, glass fiber and filler are 10-20%, 50-60%, 5-10% and 10-35% respectively, and the total mass fraction of the raw materials is 100%.

[0022] Controlling the mass ratio of diamond-silicon carbide composite abrasive, binder, glass fiber and filler within the above range can ensure that the grinding block has high strength and rigidity, can maintain a stable shape when subjected to force, and is not easy to deform. The overall strength of the grinding pad is improved, less yielding, and the chip cutting efficiency is guaranteed while ensuring the surface processing quality of the workpiece.

[0023] Preferably, the abrasive is mixed in step (2) using a vertical three-dimensional mixer, and the mixing time is 1-3 hours.

[0024] Preferably, the method for preparing the grinding pad for CVD diamond rough polishing comprises the following steps: 1) preparing a mold, wherein a plurality of grooves for forming the grinding block are provided on the mold, and the shape of the grooves matches the shape of the grinding block; The diamond-silicon carbide abrasive, binder, glass fiber and filler are mixed and stirred to form a slurry; 2) Fill the prepared slurry into each groove of the mold, and after filling evenly, apply glue, so that the glue covers the slurry filled in the groove, and then lay a layer of silk screen on the glue coated on the surface of the mold, so that the glue forms an impregnation on the silk screen, and then take a substrate with double-sided tape on one side and press it on the surface of the silk screen, and the double-sided tape layer is away from the silk screen, and finally demolding is performed after heating and curing. The silk screen impregnated with glue and the support of the substrate can ensure the integrity of the grinding block after demolding, and the glue includes epoxy thermosetting resin and inorganic powder; the inorganic powder includes any one of calcium silicate, magnesium carbonate, sodium silicate and phosphate; the silk screen is nylon silk screen or glass fiber silk screen. Nylon silk screen and glass fiber silk screen have stronger holding power on the overall particles of abrasive than non-woven fabrics. The mass ratio of epoxy thermosetting resin to inorganic powder is 6-7:3-4.

[0025] The mold is made of metal, and the grooves and chamfers on the mold are carved by laser. The metal mold has better strength and hardness than the silicone mold. In this patent, the spacing between the grinding blocks is small, which can ensure the integrity and operability of the demoulding of the grinding blocks of this special structure.

[0026] The present invention has the following beneficial effects: 1. The grinding pad structure used for CVD diamond rough polishing in the present invention is uniquely designed. Compared with the grinding blocks of ordinary grinding pads, the grinding blocks are densely distributed and the grinding area is large, which can prevent the CVD diamond from being scratched during polishing. A certain gap is retained between the grinding blocks to achieve the removal of debris; and the spacing ratio between the grinding blocks is conducive to chip removal and demolding during the grinding process, and the rounded corners are conducive to demolding during the processing, and the quality of the processed surface can also be guaranteed. The grinding blocks of the grinding pad are densely distributed and the grinding area is large, which ensures that the contact area between the grinding pad and the surface of the workpiece being processed is sufficient during the grinding process, thereby improving the surface quality of the workpiece being processed.

[0027] 2. The grinding block used for the CVD diamond rough polishing grinding pad of the present invention has a high resin content, high hardness and modulus, and extremely high toughness through a suitable raw material ratio. At the same time, a certain amount of glass fiber is added to the grinding pad system, which can ensure that the overall strength of the grinding pad is relatively high, and the shape can be kept stable when subjected to force, and deformation is not easy to occur, thereby ensuring the efficiency of grinding and polishing; the abrasive adopts a special diamond-silicon carbide abrasive (the Raman value of the raw material diamond used is above 3.0), which has high hardness, strong self-sharpening, and high grinding efficiency, and can quickly remove the sub-surface damage layer of the product, reduce additional damage to the CVD diamond, and control the roundness (the shape coefficient is 0.8-0.85). While ensuring the processing quality, the holding force of the abrasive is improved, thereby improving the polishing efficiency and service life of the grinding pad.

[0028] 3. The manufacturing process of the CVD diamond rough polishing pad of the present invention is simple, the cost is low, the equipment requirements are not high, and the polishing cycle is short, which improves the production efficiency and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a schematic structural diagram of a CVD diamond rough polishing grinding pad of the present invention; Figure 2 It is a cross-sectional schematic diagram of a CVD diamond rough polishing grinding pad of the present invention; Among them, 01-grinding block, 02-base material, 03-adhesive layer, 04-substrate layer, 05-back glue layer. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The diamond-silicon carbide composite abrasive used in the following embodiments is prepared by a method comprising the following steps: heat-insulating a mixed powder consisting of diamond grains and graphite-coated silicon grains in an oxygen-free atmosphere to gasify silicon, grinding the material obtained by the heat-insulating treatment and then naturally settling and classifying to remove impurity silicon carbide, and then washing with hydrofluoric acid to remove impurity silicon, thereby obtaining a diamond-silicon carbide composite abrasive; the diamond grains are bare diamond and / or carbon-coated diamond grains; the temperature of the heat-insulating treatment is 1400-1600° C., and the heat-insulating treatment time is 2-5 hours.

[0033] Example 1 This embodiment is used for the grinding pad of CVD diamond rough polishing, such as Figure 1 and Figure 2 As shown, it includes a base material 02 and a grinding block 01 arranged on the base material; the base material 02 includes a backing layer 05, a base layer 04, and a bonding layer 03 arranged in sequence from bottom to top, and the bonding layer 03 is formed by curing a nylon mesh impregnated with glue; the grinding block 01 is a square with a top side length of 10 mm, the spacing between adjacent grinding blocks 01 is 1 mm, and the four corners of the upper surface of the grinding block 01 have a fillet with a radius of 0.5 mm; the grinding block 01 is made of the following raw materials in mass percentage: 15% diamond-silicon carbide composite abrasive, 55% binder bisphenol A type epoxy resin, 5% glass fiber, and 25% filler; the diameter of the glass fiber used is 5μm; the filler is calcium silicate, and the D50 particle size is 2μm; the D50 particle size of the diamond-silicon carbide composite abrasive is 50μm, and the circularity is 0.80, and it is prepared by a method comprising the following steps: The first step is mixing: diamond-silicon carbide composite abrasive is mixed with diamonds with D50≈20μm and D50≈100μm, where the ratio of the three is 1:1:2 (composite abrasive: diamond powder D50≈20μm: diamond powder D50≈100μm) The second step is ball milling: pour the mixed abrasive into the mixing barrel, add a certain amount of steel balls, the total volume does not exceed 1 / 2 of the barrel, and stir it with a vertical three-dimensional mixer for 1 hour.

[0034] The third step is screening: the ball-milled abrasive is screened through 230# and 400# metal woven screens to separate the diamond-silicon carbide composite abrasive.

[0035] The fourth step is cleaning: the screened diamond-silicon carbide composite abrasive is ultrasonically cleaned and dried to obtain a diamond-silicon carbide composite abrasive with a circularity of 0.8.

[0036] The polishing pad of the present embodiment is prepared by a method comprising the following steps: 1) Prepare a metal mold, on which a plurality of grooves for forming the grinding block 01 are provided, and the shape of the grooves matches the shape of the grinding block 01; Diamond-silicon carbide composite abrasive, binder, glass fiber and filler are dispersed in a polytetrafluoroethylene tank, and a slurry is formed by double planetary mixing and stirring; 2) Fill the prepared slurry into each metal groove, scrape off the concave glue after filling evenly, and cover the slurry filled in the groove with glue, then lay a layer of nylon mesh on the glue coated on the mold surface, so that the glue forms an impregnation on the mesh, and then take a PC sheet with double-sided tape on one side and press it on the mesh surface so that the double-sided tape layer is away from the nylon mesh, and finally demold after heating and curing. The mesh impregnated with glue and the support of the PC sheet can ensure the integrity of the grinding block 01 after demolding.

[0037] Example 2 This embodiment is used for the grinding pad of CVD diamond rough polishing, such as Figure 1 and Figure 2 As shown, it includes a substrate 02 and a grinding block 01 arranged on the substrate; the substrate 02 includes a backing layer 05, a base layer 04, and a bonding layer 03 arranged in sequence from bottom to top, and the bonding layer 03 is formed by curing a nylon mesh impregnated with glue; the grinding block 01 is a square with a top side length of 15 mm, the spacing between adjacent grinding blocks 01 is 1.5 mm, and the four corners of the upper surface of the grinding block 01 have a fillet with a radius of 0.5 mm; the grinding block 01 is made of the following raw materials in mass percentage: 15% diamond-silicon carbide composite abrasive, 55% binder bisphenol S type epoxy resin, 5% glass fiber, and 25% filler; the diameter of the glass fiber used is 5μm; the filler is calcium silicate, and the D50 particle size is 2μm; the D50 particle size of the diamond-silicon carbide composite abrasive is 50μm, and the circularity is 0.80, and it is prepared by a method comprising the following steps: The first step is mixing: diamond-silicon carbide composite abrasive is mixed with diamonds with D50≈10 and D50≈90μm, where the ratio of the three is 1:1:2 (composite abrasive: diamond powder D50≈10μm: diamond powder D50≈90μmm) The second step is ball milling: pour the mixed abrasive into the mixing barrel, add a certain amount of steel balls, the total volume does not exceed 1 / 2 of the barrel, and stir it with a vertical three-dimensional mixer for 1 hour.

[0038] The third step is screening: the ball-milled abrasive is screened through 230# and 400# metal woven screens to separate the diamond-silicon carbide composite abrasive.

[0039] The fourth step is cleaning: the screened diamond-silicon carbide composite abrasive is ultrasonically cleaned and dried to obtain a diamond-silicon carbide composite abrasive with a circularity of 0.8.

[0040] The polishing pad of the present embodiment is prepared by a method comprising the following steps: 1) Prepare a metal mold, on which a plurality of grooves for forming the grinding block 01 are provided, and the shape of the grooves matches the shape of the grinding block 01; Diamond-silicon carbide composite abrasive, binder, glass fiber and filler are dispersed in a polytetrafluoroethylene tank, and a slurry is formed by double planetary mixing and stirring; 3) Fill the prepared slurry into each metal groove, and scrape off the concave glue after filling evenly. The glue is a mixture of epoxy thermosetting resin and calcium silicate, and the ratio of the two is 7:3. The glue covers the slurry filled in the groove, and then a layer of glass fiber mesh is laid flat on the glue coated on the surface of the mold to impregnate the mesh with glue, and then press the PC sheet with double-sided tape on one side on the surface of the mesh to make the double-sided tape layer away from the glass fiber mesh, and finally demold after heating and curing. The mesh impregnated with glue and the support of the PC sheet can ensure the integrity of the grinding block 01 after demolding.

[0041] Example 3 This embodiment is used for the grinding pad of CVD diamond rough polishing, such as Figure 1 and Figure 2 As shown, it includes a substrate 02 and a grinding block 01 arranged on the substrate; the substrate 02 includes a backing layer 05, a base layer 04, and a bonding layer 03 arranged in sequence from bottom to top, and the bonding layer 03 is formed by curing a nylon mesh impregnated with glue; the grinding block 01 is a square with a top side length of 10 mm, the spacing between the grinding blocks 01 is 1 mm, and the four corners of the upper surface of the grinding block 01 have a fillet with a radius of 1 mm; the grinding block 01 is made of the following raw materials in mass percentage: 15% diamond-silicon carbide composite abrasive, 55% binder bisphenol A type epoxy resin, 5% glass fiber, and 25% filler; the diameter of the glass fiber used is 5μm; the filler is calcium silicate, and the D50 particle size is 2μm; the D50 particle size of the diamond-silicon carbide composite abrasive is 50μm, and the circularity is 0.80, and it is prepared by a method comprising the following steps: The first step is mixing: diamond-silicon carbide composite abrasive is mixed with diamonds with D50≈30 and D50≈110μm, where the ratio of the three is 1:1:2 (composite abrasive: diamond powder D50≈30μm: diamond powder D50≈110μm) The second step is ball milling: pour the mixed abrasive into the mixing barrel, add a certain amount of steel balls, the total volume does not exceed 1 / 2 of the barrel, and stir it with a vertical three-dimensional mixer for 1 hour.

[0042] The third step is screening: the ball-milled abrasive is screened through 230# and 400# metal woven screens to separate the diamond-silicon carbide composite abrasive.

[0043] The fourth step is cleaning: the screened diamond-silicon carbide composite abrasive is ultrasonically cleaned and dried to obtain a diamond-silicon carbide composite abrasive with a circularity of 0.8.

[0044] The preparation method of the polishing pad of this embodiment is the same as the preparation method of the polishing pad in Example 1.

[0045] Example 4 This embodiment is used for the grinding pad of CVD diamond rough polishing, such as Figure 1 and Figure 2 As shown, it includes a substrate 02 and a grinding block 01 arranged on the substrate; the substrate 02 includes a backing layer 05, a base layer 04, and a bonding layer 03 arranged in sequence from bottom to top, and the bonding layer 03 is formed by curing a nylon mesh impregnated with glue; the grinding block 01 is a square with a top side length of 10 mm, the spacing between the grinding blocks 01 is 1 mm, and the four corners of the upper surface of the grinding block 01 have a fillet with a radius of 0.5 mm; the grinding block 01 is made of the following raw materials in mass percentage: 15% diamond-silicon carbide composite abrasive, 55% binder bisphenol S type epoxy resin, 5% glass fiber, and 25% filler; the diameter of the glass fiber used is 5μm; the filler is calcium silicate, and the D50 particle size is 2μm; the D50 particle size of the diamond-silicon carbide composite abrasive is 50μm, and the circularity is 0.80, and it is prepared by a method comprising the following steps: The first step is mixing: mix the diamond-silicon carbide composite abrasive with diamonds of D50≈20 and D50≈100, where the ratio of the three is 1:1:4 (composite abrasive: diamond powder D50≈20um: diamond powder D50≈100um) The second step is ball milling: pour the mixed abrasive into the mixing barrel, add a certain amount of steel balls, the total volume does not exceed 1 / 2 of the barrel, and stir it with a vertical three-dimensional mixer for 1 hour.

[0046] The third step is screening: the ball-milled abrasive is screened through 230# and 400# metal woven screens to separate the diamond-silicon carbide composite abrasive.

[0047] The fourth step is cleaning: the screened diamond-silicon carbide composite abrasive is ultrasonically cleaned and dried to obtain a diamond-silicon carbide composite abrasive with a circularity of 0.8.

[0048] The preparation method of the polishing pad of this embodiment is the same as the preparation method of the polishing pad in Example 1.

[0049] Example 5 This embodiment is used for the grinding pad of CVD diamond rough polishing, such as Figure 1 and Figure 2As shown, it includes a substrate 02 and a grinding block 01 arranged on the substrate; the substrate 02 includes a backing glue layer 05, a base layer 04, and a bonding layer 03 arranged in sequence from bottom to top, and the bonding layer 03 is formed by curing a nylon mesh impregnated with glue; the grinding block 01 is a square with a top side length of 10 mm, the spacing between the grinding blocks 01 is 1 mm, and the four corners of the upper surface of the grinding block 01 have a fillet with a radius of 0.5 mm; the grinding block 01 is made of the following raw materials in mass percentage: 15% diamond-silicon carbide composite abrasive, 55% binder bisphenol F type epoxy resin, 5% glass fiber, and 25% filler; the diameter of the glass fiber used is 5μm; the filler is calcium phosphate, and the D50 particle size is 2μm; the D50 particle size of the diamond-silicon carbide composite abrasive is 50μm, and the circularity is 0.85, and it is prepared by a method comprising the following steps: The first step is mixing: mix the diamond-silicon carbide composite abrasive with diamonds of D50≈20 and D50≈100, where the ratio of the three is 1:1:2 (composite abrasive: diamond powder D50≈20um: diamond powder D50≈100um) The second step is ball milling: pour the mixed abrasive into the mixing barrel, add a certain amount of steel balls, the total volume does not exceed 1 / 2 of the barrel, and stir it with a vertical three-dimensional mixer for 3 hours.

[0050] The third step is screening: the ball-milled abrasive is screened through 230# and 400# metal woven screens to separate the diamond-silicon carbide composite abrasive.

[0051] The fourth step is cleaning: the screened diamond-silicon carbide composite abrasive is ultrasonically cleaned and dried to obtain a diamond-silicon carbide composite abrasive with a circularity of 0.85.

[0052] The preparation method of the polishing pad of this embodiment is the same as the preparation method of the polishing pad in Example 1.

[0053] Example 6 This embodiment is used for the grinding pad of CVD diamond rough polishing, such as Figure 1 and Figure 2As shown, it includes a substrate 02 and a grinding block 01 arranged on the substrate; the substrate 02 includes a backing layer 05, a base layer 04, and a bonding layer 03 arranged in sequence from bottom to top, and the bonding layer 03 is formed by curing a nylon mesh impregnated with glue; the grinding block 01 is a square with a top side length of 10 mm, the spacing between the grinding blocks 01 is 1.5 mm, and the four corners of the upper surface of the grinding block 01 have a fillet with a radius of 0.5 mm; the grinding block 01 is made of the following raw materials in mass percentage: 15% diamond-silicon carbide composite abrasive, 50% binder H-type epoxy resin, 5% glass fiber, and 35% filler; the diameter of the glass fiber used is 5μm; the filler is magnesium carbonate, and the D50 particle size is 2μm; the D50 particle size of the diamond-silicon carbide composite abrasive is 40μm, and the circularity is 0.80, and it is prepared by a method comprising the following steps: The first step is mixing: mix the diamond-silicon carbide composite abrasive with diamonds of D50≈20 and D50≈100, where the ratio of the three is 1:1:2 (composite abrasive: diamond powder D50≈20um: diamond powder D50≈100um) The second step is ball milling: pour the mixed abrasive into the mixing barrel, add a certain amount of steel balls, the total volume does not exceed 1 / 2 of the barrel, and stir it with a vertical three-dimensional mixer for 1 hour.

[0054] The third step is screening: the ball-milled abrasive is screened through 230# and 400# metal woven screens to separate the diamond-silicon carbide composite abrasive.

[0055] The fourth step is cleaning: the screened diamond-silicon carbide composite abrasive is ultrasonically cleaned and dried to obtain a diamond-silicon carbide composite abrasive with a circularity of 0.8.

[0056] The preparation method of the polishing pad of this embodiment is the same as the preparation method of the polishing pad in Example 1.

[0057] Example 7 This embodiment is used for the grinding pad of CVD diamond rough polishing, such as Figure 1 and Figure 2As shown, it includes a substrate 02 and a grinding block 01 arranged on the substrate; the substrate 02 includes a backing layer 05, a base layer 04, and a bonding layer 03 arranged in sequence from bottom to top, and the bonding layer 03 is formed by curing a nylon mesh impregnated with glue; the grinding block 01 is a square with a top side length of 10 mm, the spacing between the grinding blocks 01 is 1 mm, and the four corners of the upper surface of the grinding block 01 have a fillet with a radius of 0.5 mm; the grinding block 01 is made of the following raw materials in mass percentage: 20% diamond-silicon carbide composite abrasive, 60% binder bisphenol A type epoxy resin, 5% glass fiber, and 15% filler; the diameter of the glass fiber used is 5μm; the filler is sodium silicate, and the D50 particle size is 2μm; the D50 particle size of the diamond-silicon carbide composite abrasive is 60μm, and the circularity is 0.80, and it is prepared by a method comprising the following steps: The first step is mixing: diamond-silicon carbide composite abrasive is mixed with diamonds with D50≈20 and D50≈100, where the ratio of the three is 1:1:2 (composite abrasive: diamond powder D50≈20um: diamond powder D50≈100um). The second step is ball milling: pour the mixed abrasive into the mixing barrel, add a certain amount of steel balls, the total volume does not exceed 1 / 2 of the barrel, and stir it with a vertical three-dimensional mixer for 1 hour.

[0058] The third step is screening: the ball-milled abrasive is screened through 230# and 400# metal woven screens to separate the diamond-silicon carbide composite abrasive.

[0059] The fourth step is cleaning: the screened diamond-silicon carbide composite abrasive is ultrasonically cleaned and dried to obtain a diamond-silicon carbide composite abrasive with a circularity of 0.8.

[0060] The preparation method of the polishing pad of this embodiment is the same as the preparation method of the polishing pad in Example 1.

[0061] Example 8 This embodiment is used for the grinding pad of CVD diamond rough polishing, such as Figure 1 and Figure 2As shown, it includes a substrate 02 and a grinding block 01 arranged on the substrate; the substrate 02 includes a backing layer 05, a base layer 04, and a bonding layer 03 arranged in sequence from bottom to top, and the bonding layer 03 is formed by curing a nylon mesh impregnated with glue; the grinding block 01 is a square with a top side length of 10 mm, the spacing between the grinding blocks 01 is 1 mm, and the four corners of the upper surface of the grinding block 01 have a fillet with a radius of 0.5 mm; the grinding block 01 is made of the following raw materials in mass percentage: 10% diamond-silicon carbide composite abrasive, 50% binder bisphenol S type epoxy resin, 10% glass fiber, and 30% filler; the diameter of the glass fiber used is 10μm; the filler is calcium silicate, and the D50 particle size is 5μm; the D50 particle size of the diamond-silicon carbide composite abrasive is 50μm, and the circularity is 0.80, and it is prepared by a method comprising the following steps: The first step is mixing: mix the diamond-silicon carbide composite abrasive with diamonds of D50≈20 and D50≈100, where the ratio of the three is 1:1:2 (composite abrasive: diamond powder D50≈20um: diamond powder D50≈100um) The second step is ball milling: pour the mixed abrasive into the mixing barrel, add a certain amount of steel balls, the total volume does not exceed 1 / 2 of the barrel, and stir it with a vertical three-dimensional mixer for 1 hour.

[0062] The third step is screening: the ball-milled abrasive is screened through 230# and 400# metal woven screens to separate the diamond-silicon carbide composite abrasive.

[0063] The fourth step is cleaning: the screened diamond-silicon carbide composite abrasive is ultrasonically cleaned and dried to obtain a diamond-silicon carbide composite abrasive with a circularity of 0.8.

[0064] The preparation method of the polishing pad of this embodiment is the same as the preparation method of the polishing pad in Example 1.

[0065] Comparative Example 1 The difference between the grinding pad used for CVD diamond rough polishing in this comparative example and the grinding pad in Example 1 is that the diamond-silicon carbide composite abrasive in the raw material of grinding block 01 in Example 1 is not shaped in this comparative example, and the circularity is about 0.7, and the contents not mentioned are the same as those in Example 1. The Raman value of the single crystal diamond abrasive used is also above 3.0.

[0066] Comparative Example 2 The difference between the grinding pad used for CVD diamond rough polishing in this comparative example and the grinding pad in Example 1 is that the diamond-silicon carbide composite abrasive in the raw material of grinding block 01 in Example 1 is replaced by a single crystal diamond abrasive with D50≈50μm in this comparative example, and the contents not mentioned are the same as those in Example 1. The Raman value of the single crystal diamond abrasive used is also above 3.0.

[0067] Comparative Example 3 The difference between the grinding pad used for CVD diamond rough polishing in this comparative example and the grinding pad in Example 1 is that in this comparative example, the diamond-silicon carbide composite abrasive single crystal diamond abrasive prepared in the raw material of the grinding block 01 in Example 1 is replaced with diamond with a Raman value of less than 2.0, and the contents not mentioned are the same as those in Example 1.

[0068] Comparative Example 4 The difference between the grinding pad used for CVD diamond rough polishing in this comparative example and the grinding pad in Example 1 is that in this comparative example, the ratio of each type of abrasive in the first step of the diamond-silicon carbide composite abrasive ball milling shaping method in Example 1 is adjusted to 1:1:6, and the contents not mentioned are the same as those in Example 1.

[0069] Comparative Example 5 The difference between the grinding pad used for CVD diamond rough polishing in this comparative example and the grinding pad in Example 1 is that the grinding time in the second step of the diamond-silicon carbide composite abrasive ball milling shaping method in Example 1 is set to 6 hours in this comparative example, and the contents not mentioned are the same as those in Example 1.

[0070] Comparative Example 6 The difference between the grinding pad used for CVD diamond rough polishing in this comparative example and the grinding pad in Example 1 is that in this comparative example, the chamfer of the grinding block 01 in Example 1 is set to a chamfer with a radius R=2mm, and the contents not mentioned are the same as those in Example 1.

[0071] Comparative Example 7 The difference between the grinding pad used for CVD diamond rough polishing in this comparative example and the grinding pad in Example 1 is that in this comparative example, the type of binder in the raw material of the grinding block 01 in Example 1 is replaced with polyester acrylic resin, and the contents not mentioned are the same as those in Example 1.

[0072] Comparative Example 8 The difference between the grinding layer of this comparative example and the abrasive pad of Example 1 is that the grinding pad of this comparative example has a conventional shape with a grinding block 01 having a side length of 2-3 mm and a spacing of 1.5-2 mm.

[0073] Experimental example In order to evaluate the grinding performance of the grinding pads of each embodiment and comparative example, the grinding pads of each embodiment and comparative example were subjected to a grinding experiment. The grinding machine used in the grinding experiment was a 6B single-sided grinding machine, and the grinding pressure was constant at 300 g / cm 2During grinding, the lower disc speed is 100rpm, the guide wheel speed is 30HZ, the swing frequency is 8.5HZ, the cooling medium is water, and the grinding object is polycrystalline CVD diamond that has been ground by a cast iron disc three-body grinding, with a size of 2 inches and a roughness Ra of more than 400nm; during the experiment, each embodiment or comparative example grinding pad grinds 5 batches of polycrystalline CVD diamond, 1 piece is processed in each batch, and the grinding time for each batch is greater than 30min.

[0074] After the experiment, the following parameters are used as evaluation indicators: (1) Roughness: It represents the grinding and polishing effect of the grinding pad to a certain extent. The roughness is measured by RA value, which can be directly measured by a roughness measuring instrument. The roughness of 5 points is measured for each piece of polycrystalline CVD diamond, and the average value is taken.

[0075] (2) Processing time: The processing time here is set as the time required for the roughness of the polycrystalline diamond after grinding to be below 250um.

[0076] (3) Surface damage: Grinding damage refers to the surface condition of polycrystalline diamond after grinding, which can reflect the degree of surface damage of the workpiece from a macroscopic perspective. Surface damage is determined by observation under a metallographic microscope. The damage can be divided into three levels: A-excellent, B-good, and C-poor. Grade A means the surface condition is good, Grade B means there is slight abnormal damage on the surface, and Grade C means there is more serious damage or pits on the surface.

[0077] For each test indicator, 5 test points were taken to obtain data and the average value was taken. The results are shown in the following table: .

[0078] In the process of high-speed grinding and polishing of polycrystalline CVD diamond, the grinding pad is required to meet the requirements of cutting force, self-sharpening and processing quality at the same time. The diamond grinding pads prepared in Examples 1-8 meet the requirements of polishing rate, and the processing time is short, and the surface quality meets the A-level evaluation standard. Compared with the diamond grinding pad prepared in Comparative Example 1, there is no good polishing performance of reducing roughness, the diamond in the grinding pad is not shaped, the circularity is low, the crystal form is poor, and there is abnormal damage on the surface of polycrystalline CVD. The grinding pad prepared in Comparative Example 2 has a reduced overall roughness during grinding and polishing, but the time required is longer than that of Examples 1-8, because the single crystal diamond has a higher strength, and the self-sharpening is poor compared to the diamond silicon carbide composite abrasive. At the same time, compared to the diamond-silicon carbide composite abrasive, the time required in the shaping process is longer, resulting in a reduction in the overall particle size of the diamond, which leads to an extension of the processing time.

[0079] The grinding pad prepared in Comparative Example 3 cannot effectively reduce the roughness during the grinding and polishing process, and the processing time is long. The reason is that the self-strength of the diamond used is not enough, and the polycrystalline CVD diamond cannot be effectively processed, which greatly affects the grinding and polishing effect. In Examples 1-8, the selected high-grade diamond abrasive can ensure the grinding and polishing efficiency and processing time of the grinding pad. The prepared diamond-silicon carbide composite abrasive can obtain a relatively high round abrasive through the ball milling shaping process, improve the processing quality, and the special grinding block structure can ensure that the polycrystalline CVD has sufficient contact area with the grinding block during the grinding process, further ensuring the quality of the polycrystalline CVD after grinding and polishing.

[0080] The ball milling shaping process of the diamond-silicon carbide composite abrasive used in the grinding pad of Comparative Example 4 has changed the mixing ratio of the abrasive compared to that in Example 1, and the circularity of the obtained composite abrasive cannot reach between 0.8-0.85, and the grinding and polishing effect is poor, affecting the processing quality. The time for preparing the composite abrasive ball milling shaping in Comparative Example 5 is too long, resulting in a small overall particle size of the abrasive obtained, a weak cutting force, and a longer processing time. The chamfer radius of the grinding pad prepared in Comparative Example 6 is 2mm, and the grinding and polishing time is reduced, but compared to Examples 1-8, the roughness after processing is slightly higher, the processing time is reduced, and there is a certain surface damage, because the chamfer is too large, resulting in a reduction in the contact surface with the processed CVD during the processing, resulting in high roughness and damage.

[0081] The processing time of the polishing pad prepared in Comparative Example 7 is too long because the binder used in the polishing pad in this embodiment is polyester acrylic resin, which has lower strength than bisphenol A epoxy resin. During the polishing process, the particles in the polishing block are very easy to give way, resulting in extended processing time. The shape of the polishing pad particles in Comparative Example 8 is traditional square particles, the surface of the polishing block has no chamfers, and the area is small and the spacing is large. The polishing performance is not obvious compared with Examples 1-8 in reducing the roughness, and there is serious surface damage.

[0082] In summary, the diamond polishing pads prepared in Examples 1-8 have excellent grinding and polishing performance, can effectively and quickly reduce the roughness of CVD diamond, have less surface damage, and have good processing effects; at the same time, the raw materials used in the preparation methods of Examples 1-8 are cheap and readily available, and are suitable for large-scale industrial production.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A grinding pad for CVD diamond rough polishing, characterized in that: The grinding pad comprises a base material (02) and a plurality of grinding blocks (01) with flat top surfaces arranged on the base material (02); the tops of the grinding blocks (01) are rounded; the ratio of the diameter or side length of the grinding blocks (01) to the gap distance between adjacent grinding blocks (01) is 10-15:1-1.5; the raw materials for preparing the grinding blocks (01) are: diamond-silicon carbide abrasive, a binder, glass fiber and a filler.

2. The grinding pad for CVD diamond rough polishing according to claim 1, characterized in that: The top surface diameter or side length of the grinding block (01) is 10-15 mm, the gap between adjacent grinding blocks (01) is 1-1.5 mm, and the fillet radius R of the top of the grinding block (01) is 0.5-1 mm.

3. The grinding pad for CVD diamond rough polishing according to claim 1, characterized in that: The ratio of the height of the grinding block (01) to the gap distance between adjacent grinding blocks (01) is 2-3:1; the roundness of the diamond-silicon carbide abrasive is 0.80-0.85, and the D50 particle size is 40-60 μm.

4. The grinding pad for CVD diamond rough polishing according to claim 3, characterized in that: The Raman value of the diamond raw material in the preparation of the diamond-silicon carbide powder is above 3.0; the preparation method of the diamond-silicon carbide abrasive is: the diamond-silicon carbide powder is mixed with diamonds of different particle sizes for ball milling, and the diamond-silicon carbide abrasive is obtained by screening.

5. The grinding pad for CVD diamond rough polishing according to claim 4, characterized in that: The diamonds of different particle sizes include diamond powders with particle sizes of 10-30 μm and 90-110 μm.

6. The grinding pad for CVD diamond rough polishing according to any one of claims 1 to 4, characterized in that: The binder comprises an epoxy resin polymer, and the epoxy resin polymer is bisphenol A epoxy resin, bisphenol S epoxy resin, bisphenol F epoxy resin or H epoxy resin; the diameter of the glass fiber is 5-10 μm; the filler is one or any combination of calcium silicate, magnesium carbonate, sodium silicate and phosphate; and the D50 particle size of the filler is 2-5 μm.

7. The grinding pad for CVD diamond rough polishing according to claim 1, characterized in that: The mass fractions of the raw materials diamond-silicon carbide abrasive, binder, glass fiber and filler are 10-20%, 50-60%, 5-10% and 10-35% respectively, and the total amount of the raw materials is 100%.

8. The grinding pad for CVD diamond rough polishing according to claim 1, characterized in that: The base material (02) comprises an adhesive layer (03), a base layer (04) and a back adhesive layer (05); the adhesive layer (03) is formed by curing a silk screen after being impregnated with glue; the base layer (04) is made of a PC board, a PET board or a PP board.

9. The method for preparing the grinding pad for CVD diamond rough polishing according to any one of claims 1 to 8, characterized in that: The steps include: 1) weighing the raw materials of diamond-silicon carbide abrasive, binder, glass fiber and filler according to the proportion, and mixing and stirring to form a slurry; 2) Fill the prepared slurry into each groove of the mold, then apply glue, the glue covers the slurry filled in the groove, and then lay a layer of screen on the glue, and then take a substrate with double-sided tape on one side and press it on the surface of the screen, with the double-sided tape layer facing away from the screen, and finally demold after heating and curing.

10. The method for preparing the grinding pad for CVD diamond rough polishing according to claim 9, characterized in that: The glue comprises epoxy thermosetting resin and inorganic powder; the inorganic powder is any one of calcium silicate, magnesium carbonate, sodium silicate and phosphate; the wire mesh is nylon wire mesh or glass fiber wire mesh.

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