Tham khảo tài liệu 'mems and microstructures in aerospace applications - robert osiander et al (eds) part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 324 MEMS and Microstructures in Aerospace Applications CONCLUSION Materials selection is an important consideration when designing and operating MEMS devices in the space environment. Material properties can greatly affect device performance. Table shows performance indices for various materials. Specific stiffness is a good metric for high-frequency resonating structures. Specific strength is a good metric for pressure sensor and valves. Strain tolerance is a good metric for devices which need to stretch and bend. Table also lists thermal and mechanical properties of various materials used in MEMS however the reader is reminded that real world material properties can vary widely. They are useful as a starting point but again the material properties of the MEMS materials will vary based on the fabrication processes used. The following design features and materials should be avoided 1. Large temperature coefficient of expansion mismatches unless designed as a sense or actuation mechanism 2. Pure tin coatings except that electrical or electronic device terminals and leads may be coated with a tin alloy containing not less than 3 lead only when necessary for solderability 3. Silver 4. Mercury and mercury compounds cadmium compounds and alloys zinc and zinc alloys magnesium selenium tellurium and alloys and silver which can sublime unless internal to hermetically sealed devices with leak rates less than 1 X 10-4 atm-cm sec2 5. Polyvinylchloride 6. Materials subject to reversion 7. Materials that evolve corrosive compounds 8. Materials that sublimate REFERENCES 1. Voronin V. et al. Silicon whiskers for mechanical sensors. Sensors and Actuators A Physical East-West Workshop on Microelectronic Sensors May 7-9 1991 1992. 30 1-2 p. 27-33. 2. Yun . and . DiCarlo Comparison of the tensile creep and rupture strength properties of stoichiometric SiC fibers. Ceramic Engineering and Science Proceedings Proceedings of the 1999 23rd Annual Conference on .
