A New Process and Technology for Rapid Prototyping of A μ-micro Motor *

TSINGHUA SCIENCE AND TECHNOLOGY ISSN 1007-0214 25/38 pp149-153 Volume 14, Number S1, June 2009 A New Process and Technology for Rapid Prototyping of A μ-micro Motor * ZHENG Wei ( 郑炜 ) **, ZHENG Hui ( 郑珲 ), LIAO Rui ( 廖锐 ) Department of Mechanical and Electrical Engineering, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005, China; China Telecom, Xiamen 361012, China Abstract: A new process and technology of rapid prototyping for a μ-micro motor is presented as a nontraditional machining and an advanced manufacturing technology (AMT) to be realized by using masks, including the operation principle of the motor, structure design, technique, driven circuit, and quality examination with Raman spectrum. The μ-micro motor is fabricated by the micro electro-mechanical systems (MEMS) process, the structure design must be considered to fabricate or assembly the parts during machining the motor in the meantime. The research proved that integration of IC (integrated circuit) process and MEMS using masks is effective in obtaining the rapid prototyping manufacturing of the μ-micro motor. With the mature technique to fabricate the motor, there are advantages to produce the motor in short time and with lower cost than before. The motor is a common power source of micro machines in military and civilian applications, for example, applied to micro robot, micro bio medicine, and micro machine. The size of the motor is 190 μm in maximum diameter by 125 μm in height that is bulk machined in array with the number of hundreds of micro motors on a substrate. Key words: micro motor; nontraditional machining; advanced manufacturing technology, micro-/nano- technology; micro electro-mechanical systems (MEMS); China Introduction Received: 2008-11-09; revised: 2009-03-08 * Supported by Foundation of Department of Mechanical and Electrical Engineering of Xiamen University (No. Y03001) ** To whom correspondence should be addressed. E-mail: wzheng@xmu.edu.cn; Tel: 86-592-2181786 The traditional machining has a very long history. It has great effect on the human production and matter civilization. The nontraditional machining has great role in the advanced manufacturing technology. The former consists of electrical discharge machining (EDM), electrochemical machining (ECM), laser beam machining (LBM), electron beam machining (EBM), ion beam machining (IBM), plasma arc machining (PAM), ultrasonic machining (USM), chemical machining (CHM), and rapid prototyping manufacturing (RPM), which have been the main methods of micro fine machining and micro/nano fabrication [1]. Since 1980 s when rapid prototyping came to being, it has gradually become one of the main development directions, which is composed of stereolithography (SL), selected laser sintering (SLS), selected laser melting (SLM), electron beam melting (EBML), laminated object manufacturing (LOM), three-dimensional printing (3DP), three-dimensional plotting (3D Plotting), fused deposition modeling (FDM), laser engineered net shaping (LENS), plasma deposition method (PDM), and patternless casting manufacturing (PCM) [2]. According to Prof. Ding Han, Prof. Sun Lining, Prof. Liu Baicheng, Prof. Liu Guangfu, Prof. Wang Liding, Research Fellow Wang Zhiyao s research achievement [3],

150 the six special topics have been respectively researched of the digital manufacturing, intelligent manufacturing, precision manufacturing, green manufacturing, micro/nano manufacturing, and biomanufacturing. In 1995, Prof. Yan Yongnian at Tsinghua University in China first researched the biomanufacturing [3]. With the lately achievement known from ISEM-XV that was held on April 23-27, 2007 in USA, the papers of the conference present the achievements including the newly developed methods, micro fine machining, ECM, LBM and combined machining, and the advanced development in micro fine EDM, micro fine ECM, nanofabrication, ECM, high energy beam machining (HEBM), and combined machining [4]. Having combined the RPM with micro electro-mechanical systems (MEMS) in manufacturing of micro machines, an example of the μ-micro rotary motor is given by using the masks, which is an excellent power source or actuator. 1 Operation Principle of the μ-micro The stepping motor is a type of motor which operates by attraction and expulsion of electric magnets with time varying electric pulse signals applied. The computer makes operation according to the given data and demanded functions, then sends out the electric pulse signals. After every pulse is sent by the computer, the step motor rotates a definite angle. As the pulse is sent out one by one, the step motor rotates one step by one step [5]. When the moving principle of the step motor is applied to a μ-micro rotary motor, the stators are designed to combine many shape of V with shape of Λ linked together that the magnet field is formed. With material Fe-Ni alloy, the micro motor can rotate while driven by the above pulse signals. 2 Structure Design of Rapid Prototyping of the μ-micro As shown in Fig. 1, the μ-micro rotary motor is composed of seven parts such as the lowest layer of Si(110) regarded as a support; the second layer is SiO 2. When Tsinghua Science and Technology, June 2009, 14(S1): 149-153 Fig. 1 Structure sketch of the μ-micro rotary motor (unit: mm) the micro motor is finished to fabricate, the layer must be etched by liquid HF. And then, the support is discarded. The μ-micro rotary motor is placed in a liquid. The third layer is the poly crystal silicon which is composed of six wires of electric poles which the material is Al. There are six stators shaped with which V and Λ link together and a rotor shaped like the T-shaped ring. The material of the stators and rotor is Fe-Ni alloy. The upper layer is used as a cover that material is phosphosilicate glass (PSG) to prevent the inner of μ-micro rotary motor from the dust coming in. 3 Process Design of RPM of the μ-micro References [6-9] introduce the manufacturing principle and method that the authors of these papers do not copy entirely the principle and method of others, but the bulk machining of micro and small motors is realized in array. The rapid prototyping of the μ-micro rotary motor is shown below with MEMS process, principle, design, and fabrication. 3.1 Fabrication principle The methods of deposition and lithography are used to finish the divided steps. The first step is to deposit SiO 2, poly crystalline silicon, Al wires, and Fe-Ni alloy. The second step is to lithograph the unnecessary parts. The third step is to deposit the polymer. The forth step

ZHENG Wei ( 郑炜 ) et al:a New Process and Technology for Rapid Prototyping 151 is to lithograph the surplus parts, and then deposit PSG. The upper and side position are drilled a small hole of 0.1 mm diameter on the cover of PSG. After the polymer of the upper part and around is etched, the two holes are sealed by the glue. 3.2 Process design Step 1 On the upper surface of the silicon subtract is deposited a layer of SiO 2 as an insulator layer that is again deposited a layer of polycrystalline silicon (Fig. 2a); Step 2 The six support points of μ-micro rotary motor is lithographed on the above layer of poly crystal silicon by the first mask (Fig. 2b); Step 3 The six wires of electric poles are deposited with Al alloy, the unnecessary part should be lithographed by the second mask. Step 4 After the six stators and a rotor are deposited with Fe-Ni alloy, the entire stators and a part of the rotor not including the upper part of the T-shaped-ring are lithographed by the third mask (Fig. 2c); Step 5 A layer of polymer is deposited, which has the equal level to the below surface of the T-shapedring on the rotor, and then the unnecessary part around sides must be lithographed by the forth mask; Step 6 A layer of PSG is deposited, which has the equal level to the below surface of the T-shaped-ring on the rotor, and then the unnecessary part must be lithographed by the fifth mask; Step 7 After a layer of Fe-Ni alloy is deposited, the entire rotor and shape ring are lithographed by the sixth mask; Step 8 A layer of polymer is deposited, which reaches the equal level to the below surface of the PSG cover, and then the unnecessary part must be lithographed by the seventh mask; Step 9 After a layer of PSG is deposited, the airtight cover has to be fabricated (Fig. 2d). Step 10 With the drilled methods of micro holes, two holes of upper and side surfaces of the airtight cover should be drilled in a 0.1 mm diameter, which the polymer is etched by a corrodent in order to release the rotor. Step 11 The two micro holes of 0.1 mm diameter are glued, the μ-micro rotary motor has been finished to fabricate. The space between the stator and rotor is 1-3 microns, thickness of Si substrate is 20 microns, the outside diameter of μ-micro rotary motor is 190 microns, its height is 125 microns. There are six lead wires of the motor. (a) Step 1 deposition (b) Step 2 lithograph (c) Step 4 deposition (d) Step 9 deposition Fig. 2 Rapid prototyping process diagram of the μ-micro rotary motor 4 Driven Circuit for the μ-micro As shown in Fig. 3, the electric pulse based on the computer is not directly used to control the μ-micro rotary motor. The way to put through the electric pulse must be distributed by the pulse distributor. And then, the pulse adjustor adjusts the electricity to the suitable power to drive the μ-micro rotary motor [5].

152 Tsinghua Science and Technology, June 2009, 14(S1): 149-153 Fig. 3 Principle of a driven circuit of μ-micro rotary motor Known from Fig. 4, in the pulse distributor the three phases are the phases A, B, and C, respectively. The circuit of three phases for six beats is linked with three J-K triggers to control phase exchange for the rotator running. Fig. 4 Pulse distributor in the mode of three phases for six beats 5 Raman Spectrum Detecting Technology of the μ-micro Rotary Motor The traditional methods to research the gas/solid interface mainly use the electric signal to excite and detect the spectrum, which micro research is not any satisfied on nano laser chemistry. Since 1980 s light especially such as laser is used to excite and detect the spectrum is gradually valued [9]. The Raman-STM in situ combine test system had been built by using the laser fiber, and finished the preliminary test [10-19]. The preliminary test result had shown that Raman-STM can be used to research the gas/solid system and provide a new approach to research the surface science research. This technology can be used in the laser fiber technology to monitor the fabrication process parameters. 6 Conclusions All these structures machining and assembly are fabricated by the film technology with RPM, MEMS, and IC manufacturing. The height is generally on the order of many microns and tenth microns. Compared with the side height structure on the order of many hundred microns, the above structure can only be considered as quasi 2-D structure, the space between the stator and the rotor is 1-3 microns. We have redesigned the micro motor having been designed by Prof. Ko Wen H. [6]. By one time hundreds of the μ-micro rotary motor can be rapidly prototyping manufactured at low cost and high productivity. Acknowledgements The authors would like to express their sincere thanks for financial support by the Xiamen University, Harbin Institute of Technology, Tsinghua University, and Prof. Yuyi Lin s review and constructive advices. References [1] Liu J C, Bai J C, Gao Y F. Non-Traditional Machining. Beijing: China Machine Press, 2008. [2] Yan Y N, Zhang R J, Lin F, et al. Process and developing trends of rapid manufacturing. Engineering Plastics Application, 2006, 34(Supp): 5-10. [3] Song T H, Sun L N, Yan Y N, et al. Report on Advances in Mechanical Engineering. Beijing: China Science and Technology Press, 2007. [4] Zhao W S, Gu L, Kang X M, et al. Latest advances of non-

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