I. Introduction
With the development of science and technology, higher and higher requirements are put forward for cutting processing. First, it is necessary to meet higher and higher processing efficiency, processing precision and surface quality. Secondly, it requires economical and ecological (ie green production requirements). . In order to meet these requirements, the researchers have done a lot of research work and developed a variety of advanced cutting technology, such as high-speed cutting, dry cutting, hard cutting and so on.
Microelectromechanical systems were first developed in the 1960s for integrated circuit (IC) manufacturing and materials research. Therefore, the manufacturing technology used in the development must follow the manufacturing requirements of integrated circuits, and the materials used must also It conforms to the manufacturing standards of integrated circuits, such as silicon-based materials such as polysilicon, single crystal silicon, silicon oxide, and silicon dioxide, or metals such as aluminum and copper. However, with the diversification of MEMS and micromachines, materials that traditionally meet the requirements for integrated circuit manufacturing have their limitations, and the need for microcomponents with different mechanical properties and electronic properties is becoming more and more urgent. MEMS technology has become one of the fastest growing industries in the world, and there is a large demand for industries that need to manufacture extremely small, high-precision parts, such as biology, medical equipment, optics, and microelectronics, including mobile communications and computer components. . However, not every micro-component used in MEMS or micro-mechanical applications can be produced using integrated circuit technology, so new materials and new micro-fabrication technologies and micro-cutting technologies have been developed.
Second, the scale division
For the division of scales, researchers from different research institutions and different research fields have different opinions. Materials experts believe that the scale between 10-12m and 10-9m belongs to the field of quantum mechanics research; the scale between 1 -9m and 10-6m belongs to the category of nanoscopic mechanics; between 10-6m and 10-3m The scale belongs to the category of meso-mechanics research; the scale between 1-3m and 10-0m belongs to the category of micro-mechanics research; the scale larger than 10-0m belongs to the category of macro-mechanical research. The machining discipline often uses 10-6m (1μm) as the processing error scale. The error scale of traditional machining is mostly measured by wire (1 wire = 10μm), and the error scale of precision machining can reach the micrometer level. It can be seen that the material science uses the feature length of the research object as the basis for the scale division. The machining field uses the processing precision of the research object as the basis for the division of the scale, so that the machining is divided into ordinary machining, precision machining and ultra-precision machining. There is no reference to the size of the workpiece processing feature scale.
As shown in Fig. 1, precision machining can be divided into macro-scale machining, mesoscale machining and micro-scale machining according to the dimensions of workpiece machining features. The general machining process mostly refers to macro-scale machining. The technical performance requirements of the parts are reflected on the macro-scale or surface structure. The size of the machining features is relatively large, and the processing category is wide. Micro-scale machining refers to micro-nano processing, mainly used. Precision and ultra-precision machining technology, micro-machining technology and nano-machining technology are used to emphasize “very thin cutting†and microstructure. The dimensions of processing features are relatively small, and the focus is on micro, sub-micron and nano-scale. It is the microstructure of matter; between the two is called mesoscale processing or medium-scale processing.
Figure 1 Division of precision machining scale
At present, some electromechanical products are not as small as microelectromechanical systems (micromachines) in nanotechnology, and are not as large as ordinary electromechanical products. They can be called "micromachines" for easy differentiation. The processing characteristics of micromachines span a number of different scales (see Figure 2), including microscopic scales between 10-3m and 10-0m, and mesoscales between 10-6m and 10-3m. Contains a nanoscale scale between 10-9m and 10-6m. It should be pointed out here that the processing precision that most microfabrication technologies can achieve is still in the submicron to micrometer range, and there is a big gap between the so-called nanoscale (10-10m~10-7m).
Micromachines have large markets in defense, aerospace, aerospace and civilian applications, such as tiny satellites, aircraft, machine tools, steam turbine generators, vehicles, and firearms. From the perspective of product development, miniaturization is one of its directions. Cameras, cameras, projectors, mobile phones, etc. are getting smaller and smaller, but the functions are constantly improving and perfecting. Therefore, the research of micromachining theory and technology has broad application prospects.
Figure 2 Scale scale of micromachining features
Third, micro-manufacturing technology
Micromanufacturing, which is currently used in MEMS, can be divided into micro-machining of silicon-based materials and non-silicon-based materials, which can be basically divided into four categories:
1) Etching technology
The technique utilizes dry etching, wet etching or photolithography to perform isotropic or non-isotropic etching on the material to be processed, and generally performs bulk micromachining or surface micro-processing on the material to be processed. Surface micromachining. The advantages of etching technology are high processing precision and large-scale production capacity, which is compatible with IC manufacturing, and the technology is mature. The disadvantages are fixed materials, slow processing speed, high etchant risk, and equipment funds. The investment is large and the processing environment is demanding.
2) Thin film technology
This technology mainly uses the film growth technology and etching technology to process the required microstructures. It is generally used for 2D surface micromachining and is mainly used in the manufacture of micro devices for VLSI. In addition to the mature technology and excellent IC compatibility, the thin film technology can produce a large number of micro-components without special assembly technology, and its disadvantages are the same as those of the etching technology.
3) LIGA technology
This technology combines technologies such as Deep X-Ray lithography, Micro electroforming and Micro molding. LIGA micromachining technology has high precision and good surface roughness. In addition to the advantages of good IC circuit compatibility and mass production, LIGA technology can process a wider variety of materials and better high aspect ratio 3D microstructure manufacturing capabilities than IC manufacturing technology. However, the biggest disadvantage of LIGA technology is that the cost of synchrotron X-ray required for manufacturing is extremely expensive, and the cost and time of X-ray mask are also high, so it has been used in submicron-scale microstructures. The use of cheaper LIGA-like technology to replace X-ray etching, such as UV lithography with alternative sources, excimer laser processing, and reactive ion etching (RIE), these alternatives Although the processing precision of the technology is not high in LIGA technology, the light source equipment is small and the price is relatively cheap.
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