Resonance Phenomenon and Its Effects of Laser Texture Disk

Sung Hoon Choa,Geng Wang 대한기계학회 2000 KSME International Journal Vol.14 No.7

Resonance Phenomenon and Its Effects of Laser Texture Disk

Choa, Sung-Hoon,Wang, Geng The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.7

To achieve lower flying height for high areal recording density, the laser zone texturing of the disk needs to be designed to reduce glide height. One problem of the laser bump design is that the regular laser bump pattern often produces glide resonance phenomenon, which leads to failure of the glide height test. However, it was found in this study that glide resonance is an intrinsic problem of the glide head used and resonance phenomenon depends on the type of the head slider, that is, the natural frequency of the slider body. Therefore, higher glide height or glide failure caused by glide resonance does not lead to head/media interface problem in the real drive operating conditions in which the data head is used. Pseudo-random bump pattern greatly reduces the glide resonance. Smaller bump pitch will also help to reduce the glide resonance. However, as bump spacing becomes smaller, glide height will be increased due to increased air pressure developed around the bumps. Lowering bump height is the most effect way to reduce glide avalanche.

Investigation of Durability of TSV Interconnect by Numerical Thermal Fatigue Analysis

Choa, Sung-Hoon,Song, Cha-Gyu,Lee, Haeng-Soo 한국정밀공학회 2011 International Journal of Precision Engineering and Vol.12 No.4

3D packaging using through silicon via (TSV) technology is becoming important in IC packaging industry. However, increased number of interconnects and extreme miniaturization suggest that thermo-mechanical reliability and fatigue will aggravate. In traditional package, thermo-mechanical fatigue failure mostly occurs as a result of damage in the solder joint. In TSV technology, however, the driving failure may be the TSV via or TSV interconnects. In this study, the durability of TSV technology is investigated using finite element method. Thermal fatigue phenomenon due to the plastic strain caused by repetitive temperature cycling is analyzed, and possible failure locations are discussed. In particular, the effects of via size, underfill material, and via filling material on the thermal fatigue reliability are investigated. The expected fatigue life indicates that the presence of underfill material is essential in improving the durability of the TSV structure. The plastic strain increases with the via size increases, therefore the thermal fatigue life increases as the via size decreases. For different via filling materials such as copper, nickel and tungsten, amount of plastic strain is very similar, suggesting that nickel could be used for via filling material. However, the locations of the maximum strain are different for each filling material.

Effect of Powder Synthesis Processing on the Microstructure and Electrical Conductivity of Sintered Nanocomposites

Choa Yong-Ho,Yoo Seung-Hwa,Yang Jae-Kyo,Park Jin-Woo,Oh Sung-Tag,Kang Kae-Myung,Kang Sung-Goon 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

The microstructure and electrical conductivity of CNTs dispersed nanocomposites depending on the powder processing and CNTs content were demonstrated. The composite powders with homogeneous dispersion of CNTs could be synthesized by a catalytic route for direct formation of CNTs on nano-sized Fe dispersed powders. The sintered nanocomposite using the composite powder with directly synthesized CNTs showed homogeneous microstructure and enhanced elelctrical conductivity. The influence of powder processing on the properties of sintered nanocomposites was discussed by the observed microstructural features.

HDD 디스크-스핀들 시스템의 동특성 개선에 관한 연구

좌성훈(Sung Hoon Choa),손진승(Jin Seung Sohn),이행수(Haeng Soo Lee),홍민표(Min Pyo Hong),고정석(Jeong Seok Koh),곽주영(Joo Young Kwak),조은형(Eun Hyung Cho) 한국소음진동공학회 2001 한국소음진동공학회 학술대회논문집 Vol.2001 No.6

MEMS 기술 및 소자의 국제 표준화 동향 연구

좌성훈(Choa, Sung-Hoon) 표준인증안전학회 2020 표준인증안전학회지 Vol.10 No.3

최근 IoT, Al 및 웨어러블 기술이 미래 첨단 기술로 등장함에 따라 센서 기술의 중요성이 크게 부각되고 있다. 특히, MEMS(Microelectromechanical Systems, 초소형 전기기계소자) 기술을 이용한 스마트 센서는 저전력, 소형화 및 저가격의 여러 장점으로 인해 매우 빠르게 발전하고 있다. 따라서 10 년 내에 전 세계적으로 1 조 개이상의 센서가 필요할 것으로 예상하고 있다. 또한 MEMS 기술의 빠른 발전과 함께 MEMS 기술의 표준화 요구도 크게 증가하고 있다. 1990년도에 MEMS 기술의 상용화가 시작되면서 MEMS 기술의 표준화를 위한 다양한 노력이 이루어졌다. 그러나 MEMS 소자 및 제조 공정의 다양성과 복잡성으로 인하여, MEMS 기술의 표준화는 매우 복잡하고 어려운 것으로 알려져 있었다. 본격적인 MEMS 기술의 표준화는 2008년 국제표준화 기구인 IEC에 SC 47F 위원회가 설립하면서 시작되었다. 최근에는 센서의 중요성으로 인하여 SEMI 및 IEEE와 같은 여러 기관 및 기업에서도 MEMS 표준화를 적극적으로 추진하고 있다. 본 연구에서는 주로 IEC의 표준화 활동을 중점으로 최근 진행되고 있는 MEMS 기술의 국제 표준화 및 국내 표준화 동향을 고찰하였다. 이를 통하여아직 기술 및 산업적으로 미약한 국내 센서 산업의 역량을 강화할 수 있는 방안을 제시하고자 하였다. 향후 국내의 MEMS 산업의 발전은 차세대 센서 분야인 바이오, 환경, 웨어러블 센서에 집중하고, 특히 신뢰성을 향상시킬 수 있는 기술이 필요하다. 한국의 MEMS 산업의 경쟁력 강화를 위하여 산업계와 학계가 공동으로 이와 관련된 국내의 MEMS 표준화의 개발이 시급하다고 하겠다. As IoT, Al, and wearable technologies are emerged as a future technology, the importance of the sensor technology draws a great attention. In particular, smart sensors using MEMS (microelectromechanical systems) technology have been rapidly developed due to several advantages of low power, small size, and low cost. Therefore, it was expected that more than 1 trillion sensors will be required worldwide within 10 years. Along with the rapid development of the MEMS technology, the requirements of standardization for the MEMS technology also keep rapidly increasing. As commercialization of the MEMS devices has began in the 1990s, various efforts for the MEMS standardizations has been made. However, due to the diversity of the MEMS devices and fabrication processes, the standardization of the MEMS technology has been known to be very complicated and difficult. The standardization of the MEMS technology has began in 2008 with the establishment of the SC 47F committee in IEC. Several organizations such as SEMI and IEEE are also actively promoting MEMS standardization. In this study, we reviewed the recent trends of the international and Korea standardization of the MEMS technology. It is necessary to strengthen the capabilities of the domestic sensor industry, which is still technologically and industrially weak. The future development of the domestic MEMS industry should be focus on the next-generation sensors such as bio, environment, and wearable sensors, and in particular, technologies that can improve MEMS reliability are required. In order to strengthen the competitiveness of Korea s MEMS industry, it is urgent for the industry and academia to jointly develop the related domestic MEMS standardization.

유연 ITO 박막의 신뢰성 향상을 위한 주요 인자의 실험적 연구

좌성훈(Sung-Hoon Choa),은경태(Kyoungtae Eun),오세인(Se in Oh),이미경(Mikyoung Lee),강재욱(Jae-Wook Kang),김도근(Do-Geun Kim),정성훈(Sung-Hoon Jeong) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

Transparent conducting oxide (TCO) films have recently attracted a great deal of attention due to the rapid advances being made in flexible electronic devices. However, research regarding the mechanical reliability of flexible electronics is still limited, and there is a lack of data concerning the reliability of TCO films. In this study, we investigated the bending reliability of TCO film using indium tin oxide (ITO) film on PET substrate. In order to study the effects of PET substrate thickness and ITO film thickness on bending reliability, various samples with different thickness of ITO films and substrates were fabricated and tested. The electrical and optical properties of the films were also evaluated. In order to improve the mechanical reliability of ITO film, we used the neutral mechanical plane concept, which is free from any stresses during bending. Neutral plane was made by the addition of PET substrate of the same thickness on top of the ITO/PET substrate. Finally, reliability of ITO/poly (3, 4 - ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) films was evaluated with universal reliability tests including bending, stretching, twisting, and fatigue tests.

Microstructure and Properties of Nanocomposites Prepared by Thermal CVD and Spark Plasma Sintering

Oh Sung-Tag,Choa Yong-Ho,Yoon Se-Joong,Kang Kae-Myung,Kang Sung-Goon 한국분말야금학회 2004 한국분말야금학회 학술대회논문집 Vol.2004 No.1

미세 입자에 의한 thermal asperity의 민감도 해석 및 감소 방안

좌성훈(Sung-Hoon Choa) 한국자기학회 2000 韓國磁氣學會誌 Vol.10 No.6

With use of (G)MR head, thermal asperity (TA) has been a big concern in drive industry. In this study, we investigated several factors of heads and disks which affects the TA sensitivity of the drive. TA experiments were conducted by introducing the particles on the drives using a particle injection chamber. It was found that the slider ABS shape can help to reduce TA or contamination in the head/media interface. However, TA sensitivity of the drive mainly depend on the intrinsic property of (G)MR sensor. GMR head is much less sensitive to TA compared with MR head. However, in case that the same bias current was applied for both of MR and GMR head, TA sensitivity of GMR head became almost identical to that of MR head. Therefore it was found that the bias current is a dominant factor in determining TA sensitivity of the head. TA sensitivity of different types of disks was also studied. The scratch resistance of the the carbon overcoat layer is the one of the main factors which influence TA rejection capability of the disks.

우리나라 지속가능한 국제개발협력과 기후스마트농업의 연계방안

조성제(Sung-Je Choa) 한국무역연구원 2016 무역연구 Vol.12 No.3

Millennium Development Goals have been a great strategic move to improve the quality of life as well as alleviate poverty in developing countries. However, poverty in developing countries still remains. Climate-smart agriculture is a way to achieve short-and-long-term agricultural development goals in the face of climate change and serves as a bridge to other development priorities. It seeks to support countries and other actors in securing the necessary policy, technical and financial conditions to enable them to sustainably increase agricultural productivity and incomes in order to meet national food security and development goals as well as build resilience and the capacity of agricultural and food systems to adapt to climate change. This study examines the changing trends of the new paradigm in international development cooperation through a proposal involving the activation of an international agricultural development cooperation strategy linked to agriculture, information and communication technologies and climate change. First, establish a road-map for the development model linking smart agriculture in the face of climate change. Second, develop a customized agriculture model using appropriate technology. Third, promote a knowledge-sharing project between Korea and developing countries. Fourth, establish a public-private partnership scheme