Micro Machining Technology: An Overview
Micro machining, also known as microelectromechanical systems (MEMS), refers to the development of micro-scale devices and systems that can be mass-produced. These systems integrate micromechanisms, microsensors, microactuators, signal processing circuits, and even peripheral interfaces and communication components. The key characteristics of MEMS include their small size (ranging from 1μm to 10mm), light weight, low power consumption, and high stability. They are well-suited for mass production, which significantly reduces manufacturing costs. Additionally, they exhibit high resonant frequencies, low inertia, and fast response times. Their high-tech nature and added value make them a promising field for future technological advancement.
The goal of micro-mechanics is not only to miniaturize but also to create new technologies and industries through integration, innovation, and the discovery of new principles and functional components. This technology has the potential to revolutionize various sectors, including industry, agriculture, information technology, environmental monitoring, biomedicine, space exploration, and national defense.
Microfabrication technology, a core component of micro-mechanics, involves creating mechanical devices at the microscale. It evolved closely with large-scale integrated circuits, where more electronic components are packed into smaller semiconductor areas. The minimum line width in circuit patterns is a crucial factor in improving integration levels. Microfabrication techniques allow for the creation of micro-sized components and thin-film patterns, ranging from micrometers to nanometers. These techniques are primarily based on silicon planar and bulk processing methods developed from semiconductor fabrication.
Since the mid-1980s, significant advancements have been made in micro-machining processes such as LIGA (lithography, electroplating, and molding), quasi-LIGA, micro-discharge machining (EDM), plasma beam machining, electron beam machining, rapid prototyping (RPM), and bonding technologies.
Micro-mechanical systems can perform tasks that traditional electromechanical systems cannot. When combined with electronics, they enable the mass production of low-cost, highly integrated micro-devices that find applications in numerous fields. It is expected that in this century, micro-machinery will transition from laboratories to real-world applications, significantly impacting industries like agriculture, information technology, environment, biomedicine, space, and national defense.
Micro-machining technology is a dynamic and essential field within micro-mechanics. Its development promotes interdisciplinary research and is vital for national science and technology progress, economic growth, and defense capabilities. The industrial application prospects of micro-machining are vast and promising.
Global Development of Micro-Machining Technology
In 1959, Richard Feynman introduced the concept of micro-machines, laying the foundation for the field. By 1962, the first micro-silicon pressure sensor was developed. Researchers began exploring micro-gears, micro-pumps, and micro-turbines with dimensions between 50 and 500 μm. In 1965, Stanford University developed a silicon brain electrode probe, followed by scanning tunneling microscopes and micro-sensors. In 1987, UC Berkeley created a micro-electrostatic machine with a rotor diameter of 60–12 μm, demonstrating the potential of silicon-based microfabrication for creating compact systems compatible with integrated circuits.
Governments, universities, and companies around the world have recognized the importance of micro-mechanics. In the late 1980s, MIT, Berkeley, and others published a report titled "Small Machines, Great Opportunities," emphasizing the need for U.S. leadership in this emerging field. The U.S. government allocated $50 million over five years for MEMS research, focusing on aerospace, information technology, and MEMS. NASA invested $100 million in the "Discovery Microsatellite" project, while the National Science Foundation supported MEMS research since 1998.
Japan launched a 10-year, 25-billion-yen project in 1997 to develop two prototypes for medical and industrial use. European countries also invested heavily in microsystems, with Germany pioneering the LIGA process, which became a preferred method for 3D structure fabrication. France and the European Community funded various projects, while Switzerland leveraged its precision engineering heritage to support MEMS development.
In the U.S., Caltech used microbeams to control aircraft aerodynamics, and Silicon Valley produced mass-produced accelerometers integrating sensors and circuits. Japan's micro-lathes achieved sub-micron precision, showcasing the global spread of micro-machining innovation.
Domestic Status of Micro-Machining Technology in China
China’s Ministry of Science and Technology, the National Natural Science Foundation, and other agencies have actively pursued MEMS research. Institutions like Guangdong University of Technology, Changchun Institute of Optics, and Shanghai Jiaotong University have made significant contributions. Research includes piezoelectric actuators, micro-motors, micro-pumps, and micro-robotics. Many Chinese institutions now possess the capability to conduct silicon planar and bulk processing, LIGA, micro-EDM, and stereolithography.
Development Trends in Micro-Machining Technology
Over the past decade, micro-machining has shown great potential. With its low cost and high performance, it is poised to transform industries such as biotechnology, aerospace, defense, and consumer electronics. Market demand for micro-sensors, accelerometers, and inkjet printers continues to grow, with global sales reaching $1.5 billion in 1995 and projected to reach $40 billion by 2002.
As a cross-disciplinary field, micro-mechanics benefits from advances in microelectronics, materials science, and information technology. Governments and enterprises worldwide are investing in research, ensuring continued growth. New principles, structures, and functions will emerge, leading to more intelligent and automated systems.
Key Technologies in Micro-Machining
Micro-machining involves several critical technologies:
1. **Micro-system design**: Includes database development, finite element analysis, CAD/CAM simulation, and theoretical studies on scale effects, surface phenomena, and material properties.
2. **Micro-processing**: Involves advanced lithography, LIGA, EDM, and multi-method integration to create complex microstructures.
3. **Assembly and packaging**: Focuses on bonding, sealing, and vacuum packaging for reliable micro-device integration.
4. **Characterization and testing**: Covers material property analysis, performance evaluation, and reliability assessment of micro-devices.
These technologies are essential for the continued growth and application of micro-machining in the 21st century.
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