Browsing by Author "Chung, Junwei"

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Enhancement on forming complex three dimensional microstructures by a double-side multiple partial exposure method
(2007-09-01)
Chung, Junwei
;
Hsu, Wensyang
;
機械工程學系
;
Department of Mechanical Engineering
This study presents a novel batch process based on standard lithography technology, called the double-side multiple partial exposure (DoMPE) method, which enhances the fabrication capability of three dimensional (313) photoresist micro structures. By incorporating gray-tone lithography and double-side exposure techniques, the proposed DoMPE scheme extends the multilevel morphology on both the front side and back side of the suspended photoresist microstructures. Back-side gray-tone lithography is achieved by depositing various appropriate thicknesses of Ti film on glass substrate that acts as the gray-tone mask. The process parameters, including metal film thickness, developed depth, exposure dosage, development time, and soft-bake time, are experimentally characterized. Different 3D photoresist microstructures with multiple levels on the front and back sides are successfully fabricated and presented here to show the enhancement effect using the proposed technique, including a microinductor structure and a vertical comb drive structure that demonstrate potential applications even on electrically conductive devices. (C) 2007 American Vacuum Society.
Fabrication of 3D photoresist microstructures for the polymer vertical comb drive
(2007)
Chung, Junwei
;
Hsu, Wensyang
;
機械工程學系
;
Department of Mechanical Engineering
Thick photoresist has been widely used to construct the microstructures in many micro-system applications, such as micro channels and micro molds for the electroplated metals in UV-LIGA process. Here, a simple process by combing double-side and multi-partial exposure techniques is proposed to fabricate the suspended 3D photoresist microstructures with uneven thickness. Since the development depth is determined via the control of development, exposure, and soft bake time. Experimental results indicate that longer soft bake time can achieve stable development depth under different development and exposure time. The 3D microstructures and the polymer vertical comb drive (VCD) made of thick photoresist AZ9260 (R) are fabricated here to demonstrate the proposed process. The experimental results show that the electrical conduction of the VCD can be completed by means of the Cu sputtering on the structure surface, and the electrical isolation is achieved via the undercut design.
Fabrication of a polymer-based torsional vertical comb drive using a double-side partial exposure method
(2008-03-01)
Chung, Junwei
;
Hsu, Wensyang
;
機械工程學系
;
Department of Mechanical Engineering
A novel approach which uses a double-side partial exposure method to fabricate a polymer-based torsional vertical comb drive (VCD) with thick photoresist AZ9260((R)) as the structural material is proposed in this paper. Front-side partial exposure defines the height of the fixed lower fingers, and back-side partial exposure creates the suspending space of the upper fingers, where the overlap and self-alignment between fingers can easily be achieved in this way. It does not need any sacrificial layer and etching process. A metal layer is finally deposited on the structural surface by a sputtering system for suitable electric conductivity to activate the polymer torsional VCD. The finite element method is used here to simulate the capacitance at different finger positions, and twelfth-order polynomial curve fitting is performed to obtain capacitance as a function of finger displacement. Then the rotation angle can be calculated analytically with the capacitance function. Also, the static deflection and dynamic response of polymer torsional VCDs are characterized experimentally, where the dimensions of the torsion plate are 300 mu m wide and 360 mu m long with movable fingers of length 100 mu m; the torsion spring is 60 mu m long and 4 mu m wide. Both have a thickness of 31 mu m, and the initial overlap is 11 mu m in depth and 80 mu m in length between the lower and upper fingers. By comparing the simulated and experimental results, the feasibility of the proposed fabrication method of polymer torsional VCDs is verified with a measured rotation angle of 2.31. under a driving voltage of 158.3 V.
Fabrication of polymer-based vertical comb drive using a double-side multiple partial exposure method
(2008)
Chung, Junwei
;
Huang, Yuande
;
Hsu, Wensyang
;
機械工程學系
;
Department of Mechanical Engineering
A novel approach by using a double-side multi partial exposure (DoMPE) method to fabricate the polymer-based vertical comb drive with the thick photoresist AZ9260 (R) as the structural material is proposed. With the front-side partial exposure to define height of the fixed lower fingers and back-side partial exposure to create suspending space of the upper fingers, the staggering sets of fingers with a proper initial overlap and self-alignment are easily achieved without any additional sacrificial layer. The metal layer is finally deposited on the structural surface by sputtering for the suitable electrical conductivity to activate the polymer vertical comb drive (VCD). The operation model is performed by the theoretical analysis and FEM simulation, and the static deflection and dynamic response of the polymer VCDs are characterized finally. By comparing the analytical and experimental results, the feasibility on the fabrication of polymer VCD is verified with a measured rotation angle of 2.31 degrees under the driving voltage of 158.3V.
Investigation of Ni-based thermal bimaterial structure for sensor and actuator application
(2009-02-16)
Huang, Chia-Sheng
;
Cheng, Yu-Ting
;
Chung, Junwei
;
Hsu, Wensyang
;
機械工程學系
Thermal bimaterial structures made of Ni and Ni-diamond nanocomposite for sensor and actuator application are proposed, fabricated, and tested. Two deflection types of thermal bimaterial structures, including upward and downward bending types, can be easily fabricated by controlling electroplating sequence of Ni and Ni-diamond nanocomposite. According to thermal performance measurement, the tip deflection of upward and downward types can reach about 82.5 mu m and -22.5 mu m for a temperature change of 200 degrees C, respectively. In the condition, the thermomechanical sensitivity and Output force are 412.5 nm/K and 97.0 mu N for upward type thermal bimaterial structure: and -112.5 nm/K and -26.5 mu N for downward type one. Due to the low electroplating process temperature (similar to 50 degrees C) for both Ni-based layers, diminutive pre-deformation of as-fabricated structure and strong interlaminar bonding strength are verified by SEM and vibrational test. The resonant frequency of the structure remains unchanged after 10(9) cycles. (C) 2008 Elsevier B.V. All rights reserved.
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.
Thermal bimetallic microactuators by Ni and Ni-diamond nanocomposite
(2007)
Huang, Chia-Sheng
;
Chung, Junwei
;
Cheng, Yu-Ting
;
Hsu, Wensyang
;
機械工程學系
In previous investigation, it was found that Ni-diamond nanocomposite fabricated by adding nano-diamond particles in nickel plating could enhance coefficient of thermal expansion (CTE). Here thermal bimetallic microactuators made of Ni and Ni-diamond nanocomposite are proposed, fabricated, and tested. By controlling plating sequence of Ni and Ni-diamond nanocomposite, two types of the thermal bimetallic microactuators, including upward displacement and downward displacement types, are developed. Due to the same low process temperature in electroplating these two layers, the residual thermal stress and initial deformation of. fabricated thermal bimetallic microactuators are small. Since two materials in the bimetallic actuators are Ni-based, the bonding strength between Ni and Ni-diamond nanocomposite is found to be strong. From vibration test, after 109 cycles, the resonant frequency remains unchanged. From thermal cycling test, the fabricated thermal bimetallic microactuator shows good interfacial bonding strength with only 0.002 % deviation of resonant frequency and 13.5 % deviation of tip deflection after 1,000 continuous thermal cycles.