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11.
Jong-Hwan Park Jong-Hyun Lee Yong-Ho Lee Yong-Seog Kim 《Journal of Electronic Materials》2002,31(11):1175-1180
The reaction characteristics of molten Au/Sn eutectic solder with potential diffusion-barrier materials of optoelectronic
packages were investigated. The characteristics were studied by reflowing the solder on Pt, Ni, and Co plates, respectively,
and by measuring the thickness of the reaction product. In addition, the dissolution rate of Pt into the solder was measured.
The results indicated that Pt, which is commonly used as the diffusion-barrier layer in the under-bump metallurgy (UBM) of
optoelectronic packages, reacts readily with the molten solder, resulting in discontinuous reaction products at the solder/Pt
interface. Cobalt, on the other hand, reacted with the solder at an order of magnitude slower rate than that of Pt and provided
an effective barrier against the reaction with the solder. 相似文献
12.
Jong-Seok Kim Sang-Woo Lee Kyu-Dong Jung Woon-Bae Kim Sung-Hoon Choa Byeong-Kwon Ju 《Microelectronics Reliability》2008,48(6):948-952
A micro-machined gyro chip of gyroscope is normally packaged in specific vacuum level to get the specific quality factor(Q-factor). If the Q-factor is too high, frequency tuning and the approximate matching between driving and sensing comb structure become difficult, and if the Q-factor is too low, its sensitivity decreases. The optimum Q-factor of our gyro chip design is 4000 range. To get this range, we measured the drive mode Q-factor as vacuum level of our gyro chip and we found that the vacuum level of the desired Q-factor 4000 is in the range of 740 mTorr. Based on this data, we fabricate the wafer level package gyro chip of the desired Q-factor by controlled the basic pressure of package bonding chamber just prior to the bonding process. After wafer level package process, we measured Q-factor of whole samples. Among 804 samples, 502 packaged gyro chips are worked and the Q-factor of 67% samples is between 3500 and 4500 range. 相似文献
13.
Regarding the assessment of the terrestrial food chain dose to man, radioecology may be the field that is focused on the transfer of radionuclides from environmental media to food crops. In Korea, the environmental transfer of radionuclides to staple food crops have been investigated at Korea Atomic Energy Research Institute (KAERI) for the last 25 y mainly through radiotracer experiments in greenhouses. As a result, several hundreds of parameter values for the prediction of the radionuclide transfer have been produced. Many of them appear in two recent publications of International Atomic Energy Agency. This paper outlines the KAERI's past radioecological work and introduces the ongoing research and future plans. 相似文献
14.
In situ reaction of nickel and silicon carbide has been attempted to prepare alumina-based composites containing some kinds
of dispersed phases. The composites were fabricated by reducing and sintering of Al2O3/NiO/SiC mixtures. Reaction products (Ni3Si and C) and metallic Ni were found to disperse at the matrix grain boundaries, while Ni was partly trapped into Al2O3 grains. In addition, carbon nanoballs encapsulating Ni3Si were produced and dispersed in the composites. The carbon cages were approximately 80–100 nm in diameter with polyhedral
shape, and had lattice spacing of 0.35 nm that was typical for the graphite. Encapsulated Ni3Si had facet planes which were parallel to the carbon layers surrounding. Production of metal encapsulated carbon nanoball
within ceramic materials is the first successive result that might promote researches on such novel ceramic composites.
Received: 2 January 1997 / Accepted: 15 March 1997 相似文献
15.
This paper presents an improved sensorless driving method for switched reluctance motor (SRM) using a phase-shift circuit technique. The conventional method consists of impressing short voltage pulses during unenergized phases, measuring the phase current pulses, and finding the correlation between the filtered current signals and rotor position. However, the filtering process causes a signal phase delay which varies with motor speed. This delay must be compensated for in providing the sensorless signal which is proper to the rotor position. A solution for this phase delay compensation, based on a simple analog and digital circuit, is proposed in this paper. 相似文献
16.
This paper presents novel topologies implementation for Switched Reluctance Motor (SRM) drive used in commercial applications. For effective utilization of the developed system, a novel direct current controlled PWM scheme is designed and implemented to produce the desired dynamic speed characteristic. In comparison to conventional asymmetric converter topology, it can minimize entire system costs by reducing numbers of power semiconductors. Therefore, it may open up investigation of a new way for SRM to compete with other ac motors such as induction motors, brushless dc motors, etc. The validity of the proposed method is verified through theoretical explanation and experimental results. 相似文献
17.
Zhijun Liu Gmachl C.F. Liwei Cheng Fow-Sen Choa Towner F.J. Xiaojun Wang Jenyu Fan 《Quantum Electronics, IEEE Journal of》2008,44(5):485-492
Temperature-dependent optical gain and waveguide loss have been measured for continuous-wave operated quantum-cascade lasers with wavelengths between 8.2 and 10.2 mum up to room temperature using the Hakki-Paoli method. The gain coefficient decreases with increasing temperature, and is close to the designed value for vertical transition lasers, but smaller than the designed value for diagonal transition lasers. The waveguide loss, however, is two to three times higher than calculated from free carrier absorption, and can be nearly constant, increase or decrease with temperature depending on sample design, which indicates that it is dominated by another mechanism other than plain free carrier absorption. One likely factor resulting in high waveguide loss is intersubband resonant absorption into higher lying states. 相似文献
18.
19.
Sung Min Kim Hye Ju Kim Hae Jun Jung Ji‐Yong Park Tae Jun Seok Yong‐Ho Choa Tae Joo Park Sang Woon Lee 《Advanced functional materials》2019,29(7)
A high‐performance, transparent, and extremely thin (<15 nm) hydrogen (H2) gas sensor is developed using 2D electron gas (2DEG) at the interface of an Al2O3/TiO2 thin film heterostructure grown by atomic layer deposition (ALD), without using an epitaxial layer or a single crystalline substrate. Palladium nanoparticles (≈2 nm in thickness) are used on the surface of the Al2O3/TiO2 thin film heterostructure to detect H2. This extremely thin gas sensor can be fabricated on general substrates such as a quartz, enabling its practical application. Interestingly, the electron density of the Al2O3/TiO2 thin film heterostructure can be tailored using ALD process temperature in contrast to 2DEG at the epitaxial interfaces of the oxide heterostructures such as LaAlO3/SrTiO3. This tunability provides the optimal electron density for H2 detection. The Pd/Al2O3/TiO2 sensor detects H2 gas quickly with a short response time of <30 s at 300 K which outperforms conventional H2 gas sensors, indicating that heating modules are not required for the rapid detection of H2. A wide bandgap (>3.2 eV) with the extremely thin film thickness allows for a transparent sensor (transmittance of 83% in the visible spectrum) and this fabrication scheme enables the development of flexible gas sensors. 相似文献