김봉환 교수

This paper presents track-following control using an electrostatic microactuator for super-high density hard disk drives (HDDs). The electrostatic microactuator, a high aspect ratio track-following microactuator (TFMA) which is capable of driving 0.3??g magnetic head for HDDs, is designed and fabricated by a microelectromechanical systems process. It was fabricated on a silicon on insulator wafer with a 20??m thick active silicon layer and a 2??m thick thermally grown silicon dioxide layer; a pi

The chemical and mechanical characteristics of a new surface modifier, dialkyldichloromethylsilane (DDMS, CH/sub 3/)/sub 2/SiCl/sub 2/, for stiction-free polysilicon surfaces are reported. The main strategy is to replace the conventional monoalkyl-trichlorosilane (MTS, RSiCl/sub 3/) such as octadecyltrichlorosilane (ODTS) or 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) with dichlorodisilane (DDS, R/sub 2/SiCl/sub 2/) with two short chains, especially DDMS. DDMS, with shorter chains in aproti

We examine the relation between firms’ real earnings management decisions and the slack in their net worth debt covenant. Using private debt covenant data, we find that the overall level of real earnings management is higher when net worth covenant slack is tighter. Moreover, we find that this effect is more pronounced for loan-years with the tightest slack, which is a setting where benefits of managing earnings are greater. Within the sub-sample of loan-years with the tightest slack, we find th

The current study investigated the fabrication of multi-walled carbon nanotubes (MWCNTs) adhering to Barium titanate (BaTiO3) nanoparticles and poly(vinylidene fluoride) (PVDF) nanocomposites, as well as the impact of MWCNT on the PVDF-BaTiO3 matrix in terms of dielectric constant and dielectric loss with a view to develop a high performance piezoelectric energy harvester in future. The capacity and potential of as-prepared nanocomposite films for the fabrication of high-performance flexible pie

A highly manufacturable microelectromechanical systems (MEMS) probe card was developed by using flipchip bonding technology, which is applicable to large area array bonding ranging from 2- to 8-in substrates. A cantilever-type probe structure for an actual device was electroplated with nickel-cobalt and was bonded with nickel bump, which anchored on the ceramic substrate. Gold-tin (AuSn) was used as the material of flipchip bonding between the cantilever beam and bump. Flipchip bonding itself is

We have designed and fabricated a micro-electro mechanical system (MEMS) probe card, which is suitable for a manufactured product, to achieve a deflection of 50 µm at a force of 1.5 gram (g) and a probe structure height of 720 µm. The cantilever structure consists of a tip and beam of Ni–Co, a bump of Ni and AuSn solder between them. In order to make the probe card compliant, all moving structures such as the tip, beam and bumps were electroplated with nickel, nickel–cobalt and gold solutions. T

A new microelectromechanical systems (MEMS) probe card made of electroplated nickel cantilevers, which has compliant structure, with through-wafer interconnections for IC testing is developed. The measured contact resistance was less than 0.5 ohm and leakage current was approximately 0.13 nA between tips and pads. In addition, planarity of tips and the alignment of x - and y -axes were satisfied with conventional needle probe card performance. Therefore, this probe card is suitable for wafer-lev

A vertically guided MEMS probe card was designed to deflect 50 µm at a force of 1.5 g and achieve less than 50 µm of pad pitch. Based on our experimental results, the measured average contact resistance of a device under test (DUT) was approximately 0.2 Ω at 1.44 g of force and the leakage current between two tips in the distance of one pitch was about 10 pA. In addition, tip planarity was about ±6 µm with x–y alignment errors within ±8 µm. A reliability test showed that the average contact resi

In this context, the open-circuit voltage generated by either poly (vinylidene fluoride) or PVDF and ZnO composite sample before being enhanced to 4.2 V compared to 1.2 V for the samples of pure PVDF. The spin coating method was used to create a composite film, which served as a piezoelectric nanogenerator (PNG). Zinc oxide (ZnO) nanoparticles and PVDF serve as the matrix for the coating structure. Thin films were created that employed the spin coating method to achieve the desired results of Zn

행정부가 편성한 예산은 국회의 예산심의를 통해 확정되는데 이러한 과정을 통해 예산과정의 합리성과 정치성이 조화를 이루고 있다. 이러한 제도적 장치에도 불구하고 국회의 예산심의에서 정치성이 적절한 수준에서 반영되는지에 대한 실증적인 분석연구는 많지 않다. 본 연구는 예산편성과 심의에서 정치적 목적이 예산의 효율성을 저해하지 않는지 실증적으로 분석하였다. 최근 10년간 일반회계, 특별회계, 기금을 분석한 결과 예산 효율성을 반영하는 불용액이 정치적 요인이 크게 작용하는 정권 1년 차에 다른 연차보다 높게 나타났다. 또한, 국회 심의과정에서 예산이 증가한 사업의 예산증가율이 높을수록 사업의 불용액이 높게 나타났다. 이를 통해 새롭게 들어온 정부가 지난 정부의 예산을 연속적으로 집행하기보다는 지연시키고 있으며, 국회는 정치적인 목적을 위해 준비가 미흡한 예산을 증액시키는 경향이 있음을 확인하였다. 본 연구는 불용액과 예산증가 및 감소율 간의 관계를 통해 예산편성, 심의, 집행의 전반적인 과

Real-time radiography using synchrotron radiation X-ray was utilized to directly observe and investigate the formation behavior of Fe bearing intermetallic phases in Al–Si–Cu alloys. Solidification sequences of two Al–Si–Cu alloys with different Fe content were examined in a specially designed vacuum furnace and chamber in BL20XU of SPring-8. Detailed solidification sequence and resultant phases forming reactions were confirmed by combined analyses of radiography, thermodynamic calculation and S