CN109732471B - Chemical machinery-mechanical chemistry synergistic micro grinding method and composite abrasive grain type micro grinding tool - Google Patents

Abstract

The invention discloses a chemical mechanical-mechanical chemical synergistic micro grinding method for micro parts with complex structures, such as silicon, silicon carbide, K9 optical glass and the like and silicon-based hard and brittle materials, and a composite abrasive particle type micro grinding tool used by the method. The processing method comprises the following steps: 1) corroding the modified processing layer by the grinding fluid; 2) grinding the coarse grinding particles of the grinding tool to remove the modified layer; 3) repeating the steps 1) to 2); 4) stopping supplying the grinding fluid; 5) grinding with fine abrasive grains to remove the residual layer; 6) and cleaning to remove impurities on the surface. The grinding tool is a two-stage composite abrasive particle type micro grinding tool composed of abrasive particles with different particle sizes and different types, and a smoother grinding tool is not needed in the machining process. The invention combines the advantages of chemical machinery, mechanochemistry and micro grinding processing, can realize the high geometric precision, high surface quality and high efficiency processing of silicon and silicon-based material complex structure micro parts, has simple and convenient processing method and low cost, and completely meets the requirements of industrial production.

Description

A chemical-mechanical-mechanochemical synergistic micro-grinding processing method and composite abrasive particles Micro Abrasives

technical field

The invention relates to a high-precision and high-efficiency processing method for small parts with complex structures of silicon, silicon carbide, K9 optical glass and other silicon-based hard and brittle materials, and a composite abrasive-type micro-grinding tool used in the processing method, which belongs to ultra-precision processing field.

Background technique

In recent years, with the rapid development of cutting-edge industries such as aerospace, defense industry, microelectronics industry, modern medicine and bioengineering, the demand for ultra-precise and complex structures of tiny parts, such as sensors, fluid equipment, and optical components, has become increasingly urgent. These complex structural parts have many types of materials, complex structures and high precision requirements, which impose high requirements on the corresponding manufacturing technology. Especially with the increasing application of silicon, silicon carbide, K9 optical glass and other silicon and silicon-based hard and brittle materials in ultra-precise and complex structure tiny parts, the contradiction between their processing accuracy, processing efficiency and actual demand has become increasingly prominent. The main processing methods of tiny parts of silicon-based materials are etching, photolithography, LIGA (lithography and electroforming) and other technologies based on microelectromechanical processing technology (MEMT), but these technologies have a single processing structure (two-dimensional structure), processing The efficiency is low, the processing conditions are harsh, and the cost of processing equipment is high. In addition, micro-EDM, electrochemical and other processing methods are also used for the processing of ultra-precise and complex small parts, but the processing accuracy and processing efficiency are difficult to meet the requirements, and complex three-dimensional structures cannot be processed. At present, a micro-grinding method using micro-grinding rods (also known as micro-grinding needles) has been proposed to process small parts with complex structures of hard and brittle materials, but due to the hard and brittle properties of materials, it is still impossible to solve corner cracks, chipping and surface micro-grinding. Processing damage defects such as pits, and the wear of the micro-grinding rod is very fast, and the processing efficiency is low.

Therefore, for the increasingly widely used silicon and silicon-based hard and brittle materials with complex structures and tiny parts, it is necessary to develop a new low-cost processing method with high processing accuracy, good surface quality and processing efficiency that can meet the requirements of industrial production.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a chemical-mechanical-mechanochemical synergistic microfabricator for the high geometric precision, high surface quality and high-efficiency processing requirements of silicon, silicon carbide, K9 optical glass and other silicon and silicon-based hard and brittle materials with complex structures of tiny parts. Grinding method and composite abrasive grain type micro abrasive tool.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A chemical-mechanical-mechanochemical synergistic micro-grinding processing method and composite abrasive-type micro-grinding tool, characterized in that the surface of the composite abrasive-grain-type micro-grinding tool is consolidated with two kinds of abrasives with different particle sizes and types. The grain size of the coarse abrasive grains is large, and the average cutting edge height of the coarse abrasive grains is greater than the average cutting edge height of the fine abrasive grains.

1) The surface layer of silicon and silicon-based hard and brittle materials is corroded and modified by the grinding fluid to form a silicate layer with a thickness of 1-1000 μm, and the hardness of the silicate layer is much smaller than that of the part material;

2) Rough machining is performed by the coarse abrasive particles consolidated on the surface of the tiny abrasive tool, and the silicate layer is removed by grinding, and the grinding depth or thickness is less than or equal to the thickness of the silicate layer;

3) The corrosion modification step 1) and the grinding removal step 2) are repeated until the machining is formed but a machining allowance layer of 0.1-10 μm is left, that is, the rough machining of the part is realized by chemical mechanical action;

4) Stop supplying grinding fluid;

5) Continue to use the abrasive tool for finishing, and grind to remove the machining allowance layer. The coarse abrasive grains in the abrasive tool are worn or peeled off, revealing another different kind of fine abrasive grains. This machining allowance layer contains the silicate and the material of the part itself. For the silicate, it can be removed directly; for the part material, the fine abrasive particles can react with them in the solid phase under the action of friction and friction heat to form silicate (that is, a mechanochemical reaction), and then under the mechanical action of the abrasive particles Removal down, so as to achieve the finishing of the parts by means of mechanochemical action;

6) After processing, use acetone solution, FH solution, deionized water, etc. to clean the processed parts to remove organic matter, dust and residual oxides on the surface.

The grinding fluid is an alkaline chemical solution, which can chemically react with silicon and silicon-based materials to generate silicate.

The part materials are silicon, silicon carbide, K9 optical glass and other silicon and silicon-based hard and brittle materials.

The hardness of coarse abrasive grains in the composite abrasive grain type micro abrasive tool is greater than that of silicate and is not corroded by alkaline grinding fluid, such as diamond abrasive grains; The base hard and brittle material undergoes solid-phase reaction to form silicate (that is, mechanochemical reaction occurs), such as oxide abrasive particles such as cerium oxide, magnesium oxide, and iron oxide.

The average particle diameters of the coarse and fine abrasive grains in the composite abrasive grain type micro-grinding tool differ by 1.5 to 3 times.

The coarse and fine abrasive grains in the composite abrasive grain type micro-abrasive tool are consolidated on the abrasive tool by means of complete mixing, axial spacing, circumferential spacing, spiral spacing, etc. by means of cold spraying, chemical vapor deposition, and the like.

Compared with the prior art, the present invention has the following advantages and remarkable effects:

(1) High-efficiency processing of small parts with complex structures of silicon and silicon-based materials can be realized. Processing technologies such as etching, photolithography, and micro-EDM cannot realize the processing of small parts with three-dimensional complex structures, and the processing efficiency is low. Using ultra-precision CNC machine tools, micro-grinding tools (also known as micro-grinding heads, micro-grinding rods, micro-grinding needles, etc.) micro-grinding technology, ultra-precision three-dimensional complex structure micro parts can be processed. However, when using this technology to directly process silicon and silicon-based materials, it is subject to the hard and brittle characteristics of the material. The processing depth and feed rate need to be very small, and the wear of the micro-abrasive tool is very fast, so the micro-abrasive tool needs to be replaced continuously. Processing efficiency is low. In this technical scheme, the workpiece material is corroded and modified by introducing chemical grinding fluid to form silicates with lower hardness, so a larger machining depth and feed rate can be used, and the impact force on the abrasive particles is reduced. The service life of the abrasive tool is extended, avoiding the quick replacement of the micro-abrasive tool, and effectively improving the processing efficiency.

(2) It can realize less damage-free processing of silicon and silicon-based hard and brittle materials, with high processing geometric accuracy and high surface quality. The existing micro-grinding technology is limited by the hard and brittle characteristics of the material, and cannot solve the damage defects such as corner cracks, edge chipping and surface micro-pits. However, in this technical solution, the workpiece material is corroded and modified by alkaline grinding fluid in the rough machining stage, that is, by means of chemical mechanical action, a silicate layer with a hardness far less than that of the workpiece material is formed, and the processing depth is less than or equal to the silicate layer. In actual processing, the processing depth less than the silicate layer is generally used, so as to convert the brittle fracture removal of hard and brittle materials into ductile domain removal, effectively reducing or even avoiding corner cracks, edge chipping and surface micro-pits and other processing. damage defect. In the finishing stage (that is, after the supply of grinding fluid is stopped), on the one hand, oxide abrasive grains such as cerium oxide, magnesium oxide and iron oxide and a small amount of residual rough abrasive grains are used to remove rough machining (that is, use grinding fluid for corrosion modification) The residual silicate layer; on the other hand, for the workpiece material to be processed, the oxide abrasive particles such as cerium oxide, magnesium oxide and iron oxide can react with silicon and silicon oxide in a solid phase under the action of friction and friction heat. Silicate, that is, by means of mechanochemical action, converts brittle fracture removal of materials into ductile domain removal, with high machining accuracy and surface quality. In addition, the rough abrasive grains on the abrasive tool are only a small amount left in the finishing stage due to wear or fall off in the rough machining stage, and the remaining rough abrasive grains have been passivated due to wear and will not affect the workpiece material. cause scratches. In the finishing stage, the mechanochemical reaction between the fine abrasive particles and the workpiece material produces a very small amount of a thin layer of silicate, which will not leave a residual silicate layer after grinding and removal.

(3) Extend the service life of abrasive tools and reduce the cost of processing tools. In micro-grinding, due to the hard and brittle properties of the material, the wear of the micro-grinding tool is very fast, and the micro-grinding tool needs to be replaced continuously, which reduces the processing efficiency. In addition, miniature abrasive tools, especially electroplated and sprayed micro-abrasive heads with a diameter of millimeter/sub-millimeter, are subject to the structural size and the characteristics of single-layer abrasive grains. On the one hand, this technical solution prolongs the service life of the micro abrasives by reducing the hardness of the processed object; Participate in grinding together without scratching the workpiece, further prolonging the service life of the micro-grinding tool and reducing the cost of processing tools.

(4) The processing method is simple and the cost is low. For small parts with complex structures of hard and brittle materials such as silicon and silicon-based materials, this technical solution does not require harsh processing environment, nor does it need to use expensive processing technology equipment, only need to use alkali on the existing precision CNC machining machine It can be realized by using high-performance grinding fluid and the proposed two-level composite abrasive micro-abrasive tool, and the processing method is simple. The alkaline grinding fluid used is the same as the polishing fluid used in chemical mechanical polishing (CMP) in the silicon wafer planarization technology. For example, it can be realized by mixing cerium oxide abrasive grains with a particle size smaller than that of diamond abrasive grains on an electroplated diamond micro-grinding rod, so the processing cost is low.

To sum up, the chemical-mechanical-mechanochemical synergistic micro-grinding processing method and composite abrasive-type micro-grinding tool proposed by the present invention can realize silicon, silicon carbide, K9 optical glass and other silicon and silicon-based hard and brittle materials. The ultra-precise and complex structure micro parts have high geometric accuracy, high surface quality and high-efficiency processing, and the processing method is simple and convenient, and the cost is low, which fully meets the requirements of industrial production.

Description of drawings

Accompanying drawing 1 is the flow chart of the steps of the chemical-mechanical-mechanochemical synergistic micro-grinding processing method of the present invention;

Figure 2 is a schematic view of the structure of the composite abrasive grain type micro-abrasive tool of the present invention.

Detailed ways

In order to facilitate the understanding of those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

Fix hard and brittle material parts such as silicon, silicon carbide, K9 optical glass on the machine table, clamp the compound abrasive micro-grinding tool into the spindle, and prepare the required grinding fluid. It should be noted that the grinding fluid nozzle is selected according to the characteristic size of the machined part, that is to say, the grinding fluid nozzle should be small, and the grinding fluid is supplied in a small amount, so as to avoid too much grinding fluid flowing in and corroding and modifying the non-machined parts. .

The grinding fluid nozzle is facing the front of the workpiece to be processed by the abrasive tool, and feeds at the same time as the abrasive tool, as shown in Figure 1(a). In the machining process, the grinding fluid corrodes and modifies the material of the workpiece to be machined to form a silicate layer with a thickness of 1 to 1000 μm, and the hardness of the silicate is much smaller than that of the workpiece material. Then, the abrasive tool performs rough machining on the part material, that is, the silicate layer is removed by the coarse abrasive grains, and the grinding depth or thickness is less than or equal to the thickness of the silicate layer. This transforms the brittle fracture removal mode of the material in the grinding of hard and brittle materials into a ductile domain removal mode, which not only improves the machining accuracy and surface quality of the parts, but also reduces the hardness of the machining material. The impact effect is beneficial to the prolongation of the service life of the abrasive tool. In addition, in actual processing, the grinding depth is generally less than the thickness of the silicate layer, so as to avoid machining to the workpiece material (that is, the uncorroded modified part) due to the runout of the abrasive tool. In order to improve the processing efficiency, the content and supply of *OH in the grinding fluid can be appropriately increased, and then the thickness of the corrosion-modified layer, that is, the silicate layer, can be increased, thereby increasing the grinding depth or grinding thickness.

According to the size of the complex structure to be processed by the workpiece, corrosion modification and grinding removal (that is, rough machining by the principle of chemical machining) are continuously carried out, in fact, the two are carried out simultaneously, as shown in Figure 2(a). To be processed, the basic shape is formed, but the 0.1-10μm thick machining allowance layer is reserved, and the supply of grinding fluid is stopped.

Although the supply of grinding fluid was stopped, the surface of the machined structure still had a residual silicate layer. At this time, the grinding tool is still used for finishing, as shown in Figure 1(c). In the micro-abrasive tool, limited by the structure size, the abrasive particles consolidated on the surface are very easy to wear or fall off. On the other hand, the coarse abrasive particles on the surface of the tiny abrasive tool in this technical solution are affected by the fine abrasive particles, and their quantity and consolidation depth are smaller than those of the same type of abrasive tool, so they are more likely to wear or fall off. After the coarse abrasive grains are worn or peeled off, the fine abrasive grain layer is exposed. Both the fine abrasive grains and the remaining small amount of coarse abrasive grains are capable of grinding to remove the residual silicate layer. When individual parts of the machined surface are exposed to the workpiece material prematurely due to uneven corrosion modification, the fine abrasive particles such as cerium oxide, magnesium oxide or iron oxide on the surface of the micro-abrasive tool can form a solid phase with the workpiece material under the action of frictional force and frictional heat. The reaction generates silicate (that is, a mechanochemical reaction occurs), and then it is removed by abrasive grinding, that is to say, the brittle fracture removal of the material is converted into ductile domain removal by means of mechanochemical reaction in finishing, which can not only effectively improve the parts. The machining accuracy and surface quality of the machine are improved, and it is also beneficial to prolong the service life of the micro-abrasive tool. In addition, because the fine abrasive particles such as cerium oxide, magnesium oxide or iron oxide react with the workpiece material under the action of frictional force and frictional heat, the silicate layer formed by solid-phase reaction is very small, and there is almost no residue after grinding.

Finally, use acetone solution, FH solution, deionized water, etc. to clean the workpiece to remove organic matter, dust and residual oxides on the surface. So far, all processing is completed, and the required parts are obtained, as shown in Figure 1(d).

The grinding fluid used is an alkaline chemical solution, which can chemically react with silicon and silicon-based materials to form silicates at room temperature. If you want to increase the corrosion depth or thickness, that is, the thickness of the silicate layer, the content of *OH in the grinding fluid can be increased by Fenton method, oxidative flocculation method, ozone method, ultrasonic degradation method and photocatalytic method, etc., but it depends on the workpiece. and working conditions are determined.

The surface of the abrasive tool in this technical solution is consolidated with two different types of abrasive grains with different particle sizes, so as to form a secondary composite abrasive grain type micro abrasive tool, as shown in FIG. 2 . In order to ensure the processing efficiency and prolong the service life of the abrasive tool, the hardness of the coarse abrasive grain is greater than that of the silicate and cannot be corroded by the alkaline grinding fluid. For this purpose, abrasive grains such as diamond can be used. The fine abrasive particles are required to react with silicon, silicon carbide, K9 optical glass and other silicon and silicon-based hard and brittle materials to form silicates under the action of frictional force and frictional heat. , iron oxide and other oxide abrasive particles. In order to ensure that the two kinds of abrasive grains can participate in grinding at the wrong time, the particle sizes of the two kinds of abrasive grains should be different, and the particle size of the coarse abrasive grains should be larger than that of the fine abrasive grains. When the two kinds of abrasive grains are consolidated on the surface of the abrasive tool, the average cutting edge height of the coarse abrasive grains must be greater than that of the fine abrasive grains. However, it is required that the fine abrasive particles can contact the workpiece material in time and have a solid-phase reaction after the supply of the grinding fluid is stopped, so the two kinds of abrasive particles cannot be too different, so the difference in particle size between the coarse and fine abrasive particles is 1.5 to 3 times. However, if the amount of rough machining of the workpiece is particularly large, the particle size of the coarse and fine abrasive grains can be much different. The coarse and fine abrasive grains of the abrasive tool in the example of Fig. 1 are consolidated on the surface of the abrasive tool in a mixed manner, as shown in Fig. 2(a). In fact, the coarse and fine abrasive grains of this technical solution can also be divided into axial intervals (Fig. 2(b)), circumferential intervals (Fig. 2(c)), and helical intervals (Fig. 2( Fig. 2( d)) and other ways to consolidate on the surface of the abrasive tool.

The invention mainly combines the advantages of fine grinding that can process small parts with complex structure and chemical machining and mechanochemical machining that can realize high machining accuracy and high machining surface quality of parts. The rough and finish machining of parts can be completed at one time on the precision CNC machine tool. In the roughing stage, the part material is corroded and modified by the grinding fluid, and the specific reaction principle is as follows (the reaction is similar to the principle in CMP):

(Si, SiC)+*OH+O2→SiO2+H2O+CO2

SiO2+OH-→SiO2-3+H2O

The resulting silicate is much harder than the part material, so it can be removed efficiently without sacrificing machining accuracy. In the finishing stage, the residual silicate layer can be removed by direct grinding with abrasive grains, while for the workpiece material encountered, oxides such as cerium oxide, magnesium oxide, iron oxide and other oxides exposed after being worn by the micro-abrasive tool can be used. Under the action of frictional force and frictional heat, the abrasive particles undergo a solid-phase reaction (ie, mechanochemical reaction), and a very small amount of silicate is formed (this principle has been summarized and reported in public literature, such as "Chemical Mechanical Grinding Technology Development History and Current Situation", Zhang Yifei) grinding and removal, which not only meets the requirements of high-precision and high-efficiency processing, but also has no residual modified layer. It can be seen that the present invention can fully realize the high geometric accuracy, high surface quality and high efficiency processing of silicon and silicon-based materials with complex structures of tiny parts, and the processing method is simple and convenient, with low cost, and fully meets the requirements of industrial production.

It should be noted that the above-mentioned corrosion depth, the difference in particle size between coarse and fine abrasive particles, and the size of abrasive tools are not limitations of the present invention. The replacement of diameter size, abrasive tool size, etc. are all within the protection scope of the present invention.

Claims (6)

1. a chemical-mechanical-mechanochemical synergistic micro-grinding processing method is characterized in that, the surface of the composite abrasive grain type micro-grinding tool is consolidated with two kinds of different granularities, different types of abrasive grains, and the coarse abrasive grain size is large, The average cutting edge height is greater than the average cutting edge height of the fine abrasive particles, which is used for the chemical-mechanical-mechanochemical synergistic micro-grinding processing method, comprising the following steps: 1) The surface layer of silicon or silicon-based hard and brittle materials is corroded and modified by grinding fluid to generate a silicate layer with a thickness of 1-1000 μm, and the hardness of the silicate layer is much smaller than that of the part material; 2) Rough machining is performed by the coarse abrasive particles consolidated on the surface of the tiny abrasive tool, and the silicate layer is removed by grinding, and the grinding depth or thickness is less than or equal to the thickness of the silicate layer; 3) The corrosion modification step 1) and the grinding removal step 2) are repeated until the machining is formed but a machining allowance layer of 0.1-10 μm is left, that is, the rough machining of the part is realized by chemical mechanical action; 4) Stop supplying grinding fluid; 5) Continue to use the abrasive tool for finishing, and remove the machining allowance layer by grinding. The coarse abrasive grains in the abrasive tool are worn out or fall off, revealing another different kind of fine abrasive grains. Dull coarse abrasive grinding removes the machining allowance layer. The machining allowance layer contains silicate and the material of the part itself. For the silicate, it can be removed directly; Under the action, it can have a mechanochemical reaction with it to generate silicate, which is then removed under the mechanical action of abrasive particles, so as to realize the finishing of the parts by means of mechanochemical action; 6) After processing, use acetone solution and deionized water to clean the processed parts to remove organic matter, dust and residual oxides on the surface. 2. A chemical-mechanical-mechanochemical synergistic micro-grinding method according to claim 1, wherein the grinding fluid is an alkaline chemical solution that can react chemically with silicon or silicon-based materials to generate silicon acid salt. 3 . The chemical-mechanical-mechanochemical synergistic micro-grinding method according to claim 2 , wherein the material of the part is a silicon or silicon carbide-silicon-based hard and brittle material. 4 . 4. A chemical-mechanical-mechanochemical synergistic micro-grinding processing method according to claim 1, characterized in that, the coarse abrasive grains of the composite abrasive-grain type micro-grinding tool are those whose hardness is greater than that of silicate and are not affected by alkali. diamond abrasive grains corroded by abrasive cutting fluids; the fine abrasive grains are cerium oxide, magnesium oxide or iron oxide that undergo a mechanochemical reaction with silicon or silicon-based hard and brittle materials to form silicates under the action of frictional force and frictional heat Abrasive. 5 . The chemical-mechanical-mechanochemical synergistic micro-grinding method according to claim 4 , wherein the average particle diameters of the coarse and fine abrasive grains of the composite abrasive-grain-type micro-grinding tool differ by 1.5 to 3 times. 6 . 6. A chemical-mechanical-mechanochemical synergistic micro-grinding processing method according to claim 5, characterized in that the coarse and fine abrasive grains are consolidated in a complete mixing, axially spaced, circumferentially spaced or helical spaced manner. on the grinder.

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