Sung-Il Chung

Evaluation of micro-replication technology using silicone rubber molds and its applications

Micro-replication technology (MRT) originated in semiconductor processes and has been widely utilized in other industries such as sensors, micro-fluidics and displays. Recently, however, MRT has been slow in spreading due to its high cost and material limitations. Therefore, a new process in this paper, for MRT using silicone rubber molds is introduced. In this process, a silicone rubber mold transfers a master pattern to the final product with the same shape but different material. In order to verify the possibility of applying silicone rubber molds to MRT, its transferability was evaluated, and then was applied to the fabrication of PDP barrier ribs.

Analysis of a dynamic speaker in mobile phones by considering mechanical, electrical, and magnetic coupling effects

With the advent of 3G mobile phones, a combined laptop personal computer and mobile phone can be realized that enables multimedia data communication such as TV streaming, web searching, music play, etc. A dynamic speaker is an essential part to generate high quality sound in the next generation mobile phones. Noting that characteristics of a dynamic speaker are a coupled phenomenon of mechanical, electrical, and magnetic system, a systematic analysis must be implemented to fully consider the coupling effects for an improved design. This paper presents a complete analysis of a dynamic speaker by considering mechanical, electrical and magnetic coupling effects. Results of the analysis are confirmed by the experiments. An improved design of a dynamic speaker is also proposed with enhanced performance.

Rapid fabrication of aluminum shoe mold using vacuum sealed casting process

Abstract Rapid prototyping and manufacturing (RP&M) is the most appropriate technology for the small-lot production system, because the production cycle is getting shorter owing to various needs of the consumer. Recently RP products, which are made of plastics, wax, and paper, were used to examine the design of samples. These samples, however, cannot be applied to the real mold because soft materials, such as plastics lack the necessary strength to be a mold. So the materials have been changed from RP products to a metal powder filled mold like an epoxy-metal powder composite mold or metal mold, which is called rapid tooling (RT) technology. In this paper, RT technology is applied to the casting process. The casting process has the ability to reflect complicated shapes in one process. But it has not been widely used to make a die and mold because of the poor surface quality caused by air bubbles on the surface of the casting product. In this study, the porous casting mold is fabricated from a mixture of ceramic powder and water-soluble binder. The porous casting mold can improve the characteristics of aluminum casting products with the help of the vacuum sealed casting process. The vacuum sealed casting process is an advanced technology that removes the air bubbles between the porous casting mold and the liquid metal, thus making the surface of the aluminum casting product finer. The purpose of this paper is to develop a high quality shoe mold using porous casting mold and to apply the RP&M technology to the shoe industry.

Development and manufacturing of hexahedral type vibration motor used for mobile phone

Abstract Mobile communication industry powered by electronics and information technology is building a transforming way for human communication. The latest electronics is so saturated to forget the difficulty in size reduction of electronic parts. However, mechanical parts, such as dynamic speakers and vibration motors, are intrinsically not easy to realize size reduction due to their construction. In this paper, a hexahedral type with simpler configuration is introduced and manufactured to substitute for the conventional vibration motors. After an analysis of magnetic and mechanical characteristics, it is shown that the coil configuration is the most important parameter to increase the output torque, and thus vibration. For optimization, genetic algorithm is used to find the optimal configuration of coil to maximize the output torque. Also, to analyze and manufacture a hexahedral housing case of these components, the FE analysis is carried out. A systematic approach is established for the design of the forming processes for hexahedral housing cases. Some results of the FE analysis for magnetic and mechanical characteristics are confirmed by those from a series of experiments.

A Study on the Manufacture of the Next Generation CMP Pad with a Uniform Shape Using the Micro-Molding Method

Polishing processes are widely used in the glass, optical, die, and semiconductor industries. Chemical-Mechanical Polishing (CMP) is especially becoming one of the most important ULSI processes for the 0.25 μm generation and beyond. CMP is conventionally carried out using abrasive slurry and a polishing pad. But the surface of the pad has irregular pores, so there is non-uniformity in slurry flow and in contact area between wafer and the pad causing glazing on the surface of the pad. This paper introduces the basic concept and fabrication technique of the next generation CMP pad using hydrophilic polymers with swelling characteristics in slurry, and explains the self-conditioning phenomenon and the micro-molding method used to obtain uniform protrusions and pores on the pad surface. Experimental results demonstrated the swelling characteristics, the hardness, and the accuracy of the form of the developed pad.

Fabrication of Real 3D Shape Components Using Bi-Sn Alloys

In this paper, new replication techniques fur a metal microcomponent having a real 3D shape were introduced. Helical gear was selected as one of a real 3D microcomponents for this study. The helical gear, which was made of photo-curable resin, was fabricated as a master pattern by microstereolithography technology. Then, a silicone rubber mold was fabricated from the master pattern. Lastly, a final bismuth alloy pattern was transferred from the silicone rubber mold by the microcasting process. In this paper, the replication technique is described in detail from the master pattern to the final pattern with some investigation on factors related to the technique.

Development of Rapid Tooling Technology for Shoe Mold and Its Applications

RP&M (Rapid Prototyping and Manufacturing) is the most appropriate technology for the small-lot production system, because the production cycle is getting shorter owing to various needs of the consumer. In this paper, rapid tooling technology is applied to the casting process. The casting process has the ability to reflect complicated shapes in one process. But it has not been widely used to make a die and mold because of the poor surface quality caused by air bubbles on the surface of the casting product. In this study, the porous casting mold is fabricated from a mixture of plaster and water-soluble binder. The porous casting mold can improve the characteristics of casting products with the help of the vacuum sealed casting process. The vacuum sealed casting process is an advanced technology that removes the air bubbles between the porous casting mould and the liquid metal, thus making the surface of the casting product finer. The purpose of this paper is to develop a high quality shoe mold using porous casting mold and to apply the RP&M technology to the shoe industry.

Development of Micromolding Technology using Silicone Rubber Mold

Microsystem technology (MST) which originated from semiconductor processes has been widely spreaded into the other industry such as sensors, micro fluidics and displays. The MST, however, has been troubled in spreading with its high cost and material limitations. So, in this paper, new process for micromolding technology using silicone rubber mold was introduced. Silicone rubber mold, which was fabricated by vacuum casting, can be transferred a master pattern to a final product with the same shape but different materials. In order to verify the possibility of application of silicone rubber mold to the MST, its transferability was evaluated, and then it applied to the fabrications of polishing pad and PDP barrier ribs.