Browsing by Author "Yeh, Cheng-Chi"

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Design and fabrication of a cascaded electro-thermal bimorph actuator
(2005)
Lin, Chen-Hsuan
;
Yeh, Cheng-Chi
;
Hsu, Chen-Peng
;
Hsu, Wensyang
;
機械工程學系
Here a cascaded bimorph actuator is proposed by integrating several novel actuation units to accumulate the vertical displacements. Each actuation unit comprises two types of bimorph beams and a constraint bar, and both beams will stretch outward with respect to the constraint bar while heating. In comparison with other three conventional bimorph actuator designs at the same device size, it is shown that the proposed design can provide larger vertical displacement. The proposed cascaded bimorph actuator is fabricated by surface micromachining technique and released by XeF2 silicon isotropic etching. Whole suspended structure consisting of the polysilicon and the aluminum is around 510 x 400 mu m(2) with four actuation units. The resistance is about 650 Q. In testing, the fabricated device is shown to provide reversible vertical displacement of 22.5 mu m at 4.5 V, and the operating temperature is measured by an infrared thermal microscope (InfraScope II, QFI). The calibrated maximum temperatures are compared with simulated results by ANSYS 6.0 in good agreement. It is found that the maximum temperature is 147 degrees C when the input voltage is 4.5 dc volts, and the maximum temperature is below 400 degrees C even at 10 V. However, it is found that the residual stress in the suspended structure will affect the vertical displacement of the device.
Experimental investigation and characterization of micro resistance welding with an electro-thermal actuator
(2009-02-01)
Chang, Chun-Wei
;
Yeh, Cheng-Chi
;
Hsu, Wensyang
;
機械工程學系
;
Department of Mechanical Engineering
Resistance welding is a common scheme of assembly on the macro scale by pressing together two workpieces with current passing through them to generate joule heating at the contact region due to high contact resistance. However, micro assembly by resistance welding is seldom reported. Here, resistance welding with an electro-thermal microactuator to assemble micro Ni structures is experimentally investigated and characterized. The bent-beam electro-thermal microactuator is designed to provide the necessary displacements and pressing forces. The two-mask metal-based surface micromachining process is adopted to fabricate the micro Ni structures. The calibrated initial contact resistance is shown to decrease with increasing contact pressure. Furthermore, stronger welding strength is achieved at a smaller initial contact resistance, which indicates that a larger clamping force would enhance the welding strength as large as 3.09 MPa (74.4 mu N) at a contact resistance of 2.7 Omega here. The input welding energy is also found to be a critical factor. In our tests, when welding energy is below the threshold limit of 0.05 J, the welding trials all fail. For the energy between 0.05 J and 1 J, there is a transition from a lower yield of 33.3% to a higher yield of 58.3%. At high welding energy, between 1 and 10 J, 100% yield is achieved. With the demonstration and characterization of micro resistance welding by the electro-thermal microactuator, the scheme proposed here would be helpful in the automation of micro assembly.
Micro assembly by micro resistance welding with electro-thermal actuators
(2007)
Yeh, Cheng-Chi
;
Chung, Junwei
;
Chang, Chun-Wei
;
Hsu, Wensyang
;
機械工程學系
Here micro resistance welding to assemble micro Ni structures with electro-thermal micro actuators is proposed and demonstrated. Since the contact point of two structures will have large contact resistance, high local temperature can be generated with current passing through due to joule heating. In order to move the micro structure and provide welding pressure to generate proper contact resistance between two micro structures, bent-beam electro-thermal actuators are used here. By proper design on the size and the number of actuators, the feasible operation parameters on contact resistance and pressure are identified. It is shown that micro resistance welding can be achieved with the contact resistance from 4.6 Omega to 12 Omega at the contact pressure from 7.2 to 39.3MPa.