Browsing by Author "Chen, RH"

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Development behaviours and microstructure quality of downward-development in deep x-ray lithography
(2001-11-01)
Cheng, CM
;
Chen, RH
;
機械工程學系
;
Department of Mechanical Engineering
This paper presents a novel development method for fabricating high aspect ratio microstructures in deep x-ray lithography. In this method, microstructures are developed downward to utilize the difference of the specific weight between the development products and the developer to efficiently remove the development products. The development behaviours of the proposed method (downward-development) are investigated and compared with the conventional method (upward-development). Experimental results indicate that the developing rate of downward-development is approximately twice that obtained by upward-development. Additionally, the development products are easily removed and a satisfactory microstructure quality is achieved via this process. The proposed method also yields accurate predictability to estimate the necessary developing time. Moreover, the elevated temperature increases the developing rate of downward-development more sensitively than for upward-development.
Effect of gravel subgrade on hydraulic performance of geosynthetic clay liner
(2003-12-01)
Shan, HY
;
Chen, RH
;
土木工程學系
;
Department of Civil Engineering
The effect of a gravel subgrade on the hydraulic performance of GCLs is investigated. Laboratory test results show that the GCL specimens exhibit significant variation in thickness when compressed against gravel. The maximum and minimum thicknesses of the specimen were about 20 and 3 mm, respectively, after consolidation by an effective stress up to 138 kPa. However, the permittivity of GCLs remained very low. The permittivity of both needle-punched and adhesive-bonded geotextile-supported GCLs decreased with increasing confining stress, regardless of the type of subgrade materials. In general, larger particles led to more significant migration of bentonite. Nevertheless, there was no significant difference in the degree of bentonite migration between the two GCLs investigated. (C) 2003 Elsevier Ltd. All rights reserved.
Experimental investigation of fabrication properties of electroformed Ni-based micro mould inserts
(2004-11-01)
Cheng, CM
;
Chen, RH
;
機械工程學系
;
Department of Mechanical Engineering
In this work, Ni and Ni-Fe micro mould inserts with high aspect ratios are fabricated by Si-LIGA. Many analyses were performed to elucidate the material properties of Ni-based micro mould inserts. The surface properties were examined using a scanning probe microscope (SPM). Nanoindentation was used to measure the elastic modulus and hardness of Ni-Fe microstructures. When the iron content of Ni-Fe micro mould inserts exceeded 12%, the grain size of the Ni-Fe alloy was under 15 nm. Additionally, the mechanical properties of Ni-based microstructures obtained by electroformng are superior to those obtained by casting or powder metallurgy. Satisfactory electroforming current densities for obtaining a mould insert with a fine surface profile ranged from 4 ASD to 6 ASD. (C) 2004 Elsevier B.V. All rights reserved.
Fabricating a micromould insert using a novel process
(2005)
Chen, RH
;
Chang, CC
;
Cheng, CM
;
機械工程學系
;
Department of Mechanical Engineering
A new method of fabricating micromould inserts that is compatible with semiconductor manufacturing is proposed. Diffusion of phosphorous at a high temperature is first used to increase the electric conductivity of the surface of the silicon wafer to generate a silicon-based seed layer for electroforming. If the process temperature and the duration of doping with phosphorous are controlled, then the electric conductivity of this novel silicon-based seed layer can be expected to equal that of a metal seed layer. Then, a structure layer of amorphous silicon is successfully formed onto the silicon-based seed layer, by plasma enhanced chemical vapor deposition (PECVD). The structure layer has none of the defects that would be present if a metal seed layer were used to replace the silicon-based seed layer. Finally, a silicon-based master microstructure was created by using ICPRIE to etch the structure layer. The silicon-based master has been demonstrated to be useable in successfully fabricating, by electroforming, a metal micromould insert with a large area and high aspect ratio.
Fabrication of high-aspect-ratio ceramic microstructures by injection molding with the altered lost mold technique
(2001-03-01)
Chen, RH
;
Lan, CL
;
機械工程學系
;
Department of Mechanical Engineering
A fabrication process for complex ceramic microstructures was proposed that combines a lost mold technique and ceramic injection molding. Two key points in this process were studied. First, the solubility of several engineering plastics in various organic solvents was tested to find appropriate combinations of mold material and solvent for dissolving molds, Secondly, the binder extraction rate and the strength of a green body during debinding were investigated. Experimental results indicate that acrylonitrile-butadiene styrene and acetone are the best combinations selected for this lost mold technique. We also propose that using gasoline as the debinding solvent and performing the debinding at room temperature mill give a good time-saving effect and avoid toppling the microstructure if paraffin wax, stearic acid, and polyethylene were selected to compound the binder system. This process has been successfully applied to fabricate several ceramic microstructures, such as integrated punch.
Finite element analysis of hot embossing of polymer optical sheet
(2003)
Lin, CR
;
Chen, RH
;
Hung, C
;
機械工程學系
;
Department of Mechanical Engineering
Finite element simulation of the hot embossing process used in manufacturing polymer optical components was performed using MARC code. This research focuses mainly on predicting contractive deformation during the cooling procedure in making a polymer optical sheet. A nonlinear viscoelastic model of temperature and pressure-dependent material properties, exhibiting creep, was used to capture the properties of amorphous polymer material. The simulation of contractive deformation confirms with the results of corresponding experiments, indicating that this finite element model can be used to simulate the hot embossing of a polymer with acceptable results.
Improving spin-coating process using altered cover design
(2004-12-01)
Cheng, CM
;
Chen, RH
;
機械工程學系
;
Department of Mechanical Engineering
A novel work chamber cover design for a spin coater that can reduce the effect of airflow on spin coating is presented. The experimental results reveal that superior uniformity and film area can be obtained by utilizing the modified design instead of the conventional design.
Injection molding of polymer micro- and sub-micron structures with high-aspect ratios
(2006-05-01)
Liou, AC
;
Chen, RH
;
機械工程學系
;
Department of Mechanical Engineering
This work studies the injection molding characteristics of polymer micro- and sub-micron structures using demonstration mold inserts with micro- and sub-micron channels with high-aspect ratios. The effects of the injection molding parameters on the achievable aspect ratio of the micro- and sub-micron walls were investigated. Additionally, distinctive mold-filling behaviors and resulting defects were observed for various polymers, such as polymethyl methacrylate (PMMA), polypropylene (PP) and high-density polyethylene (HDPE). Experimental results reveal that the mold temperature determines the success of the injection molding of micro- and sub-micron walls. The satisfactory mold temperature for micro-injection molding significantly exceeds that for traditional injection molding. Moreover, the main injection pressure and the main injection time substantially affect the achievable aspect ratio of the micro- and sub-micron walls. Furthermore, unusual flow behaviors occur and poor molding results are obtained when PP and HDPE are used for micro-injection molding.
Key issues in fabricating microstructures with high aspect ratios by using deep X-ray lithography
(2004-05-01)
Cheng, CM
;
Chen, RH
;
機械工程學系
;
Department of Mechanical Engineering
High aspect ratio microstructures are frequently made with the Lithographie, Galvanoformung, Abformung (LIGA) process. The success of this process depends critically on "deep" X-ray lithography (DXRL). This paper presents a variety of experimentally and analytically determined techniques for optimizing DXRL. These include methods for designing and fabricating high-quality X-ray masks. Methods for optimizing the exposure dosage and developing cycle are described. New methods for promoting resist adhesion and for avoiding resist film cracking are discussed. The influence of developer surface tension on the resist solvation process is quantified and new methods for controlling this surface tension are described. (C) 2004 Elsevier B.V. All rights reserved.
Shrinkage properties of ceramic injection moulding part with a step-contracted cross-section in the filling direction
(2004)
Chen, RH
;
Ho, CH
;
Fan, HC
;
機械工程學系
;
Department of Mechanical Engineering
The need for ceramic materials in microelectromechanical systems (MEMS) is increasing quickly. A typical form of designed ceramic micro parts involves the structuring of several micro columns and/or thin walls on a substrate. This work considers the use of a model mould with a straight mould cavity and a step-contracted cross-section in the filling direction. The injection moulding of such of ceramic micro part is experimentally simulated. The effect of the mould cavity contraction ratio, moulding conditions, and the solid loading of the ceramic/binder mixture on the distribution of the transverse shrinkage of the moulding parts at moulded, debinded, and sintered stages, respectively, are examined. Experimental results reveal that transverse shrinkage of the region downstream from the step-contracted cross-section clearly exceeds that of the region upstream in all three stages. Furthermore, transverse shrinkage varies greatly in the plane of the step-contracted cross-section. The magnitude of the variation in transverse shrinkage in the step-contracted cross-section increases with the contraction ratio of the mould cavity. Appropriately increasing either the holding pressure or the filling pressure of the mould cavity reduces the variation in the transverse shrinkage of the step-contracted cross-section. Moreover, using the ceramic/binder mixture with a composition similar to that of critical solid loading can lower the internal stress caused by sintering in the vicinity of the step-contracted cross-section. (C) 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Study of spin coating properties of SU-8 thick-layer photoresist
(2001)
Chen, RH
;
Cheng, CM
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機械工程學系
;
Department of Mechanical Engineering
In this paper the coating properties including film thickness, thickness uniformity and variation of viscosity of SU8 photoresist were investigated by using a spin coater and rheometer. Experimental results indicate that the coating qualities of SU8 are affected by several factors including the spinning speed, the photoresist viscosity, the initial acceleration and the duration. Some recommendations are presented for increasing the quality of SU8 spin coating in thick-film processing.
The characterisation and finite-element analysis of a polymer under hot pressing
(2002)
Lin, CR
;
Chen, RH
;
Hung, C
;
機械工程學系
;
Department of Mechanical Engineering
Finite-element simulation of the hot pressing process has been performed using ABAQUS. The viscoelastic polymer (polymethyl methacrylate) used in this study has mechanical properties that depend on the temperature and working pressure. Based on the nonlinear viscoelastic model, the polymer material behaviour is simulated successfully with the data obtained from material tests. Simulation results conform to related experiments, indicating that the approach can accurately predict pressure distribution within a polymer hot pressing.