• Journal of the Korean institute of surface engineering
• /
• v.48 no.6
• /
• pp.253-259
• /
• 2015

The test equipment becomes more important with the development of semiconductor industry. MEMS probe is an important testing component to detect the defects from the generated electric signal when it contacts the metal pad of semiconductor devices. Ni-Pd alloy has been paid attention to as a candidate of MEMS probe material because of its high surface hardness and relatively low resistivity. In this study, electroplated Ni-Pd alloy has been prepared by using ethylene diamine as a complexing agent. Solid solution alloy coating could be formed when concentration of palladium chloride and current density were in the ranges of 1~5 mM and $0.2{\sim}1.5A/dm^2$, respectively. The increase of current density brought about an decrease in palladium content, which made both of lattice parameter and grain size smaller. As a result of grain refinement, high hardness could be obtained. However, surface cracking was observed due to residual stress when the current density was above $1.3A/dm^2$. When effects of heat treatment temperature on hardness and sheet resistance were investigated, the accompanied grain growth decreased both of them. The decrease of hardness remained stable at a temperature of $200^{\circ}C$. The sheet resistance was drastically reduced at $100^{\circ}C$. After that, it was found to become constant.

• Journal of the Korean Ceramic Society
• /
• v.18 no.2
• /
• pp.99-104
• /
• 1981

Glass-ceramics possessed a number of characteristics which suggested their suggested their use for sealing to metals. The choice of particular glass-ceramics compositions for this application is governed by various factors, including workability of the glasses, thermal expansion characteristics and the matching of these to appropriate metals. Other properties, such as mechanical strength, determined the performance of glass-ceramics to metal seals. The purpose of the present study was to investigate direct sealing behaviour of copper to $Li_2O-ZnO-SiO_2$ system glass-ceramics. The design of the seal was a concentric seal which might contribute to the strong bond formation by providing compressive stress during thermal excursions. Tensile strengths of sealing layers were measured by Instron test machine. The layers were examined by electron probe microanalyzer. Crsystallization rate was increased with the amount of ZnO or $Li_2O$, and ZnO increased the sealing strength, but $Li_2O$ lowered it. Sealing mechanism was due to the formation of metal oxides, which acted as binder between copper and glass-ceramics. The nickle-plated copper seal with 10% $Li_2O$ and 30% ZnO was the most strong seal, and its sealing strength was more than 56kg/$\textrm{cm}^2$.

• Journal of the Microelectronics and Packaging Society
• /
• v.13 no.2 s.39
• /
• pp.21-26
• /
• 2006

We developed a bonding at low temperature using fine pitch Sn and In bumps, and studied the reliability of the fine pitch In-Sn solder joints. The $30{\mu}m$ pitch Sn and In bumps were joined together at $120^{\circ}C$. A non conductive adhesive (NCA) was applied during solder joining. Thermal cycling test ($0^{\circ}C-100^{\circ}C$, 2 cycles/h) of up to 2000 cycles was carried out to evaluate the reliability of the solder joints. The bondability was evaluated by measuring the contact resistance (Rc) of the joints through the four point probe method. As the content of filler increased, the reliability improved in the solder joints during thermal cycling test because the contact resistance increased little. The filler redistributed the stress and strains from the thermal shock over the entire joint area.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.5
• /
• pp.501-509
• /
• 2001

For the enhancement of ECT reliability on the primary water stress corrosion cracks of nuclear steam generator tubes, of which the occurrence is on the increase, it is important to comprehend the signal characteristics on crack morphology and to select an appropriate probe type. In this paper, the sizing accuracy and the detectability for the inner wall axial cracks of tubes were quantitatively evaluated using the following specimens: the electric discharge machined notches and the corrosion cracks which were developed on the operating steam generator tubes. The difference of eddy current signal characteristics between pancake and axial coil were also Investigated. The results obtained from this study provide a useful information for more precise evaluation on the inner wall axial tracks oi stram generator tubes.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.3
• /
• pp.21-27
• /
• 2012

Estimating the thermal conductivity of clayey soils is important for enhancing the performance of geoengineering structures in cold regions and clay barriers for nuclear waste repositories, but specimen disturbance, saturation, and heat boundary conditions of the test apparatus hinder reliable measurements of the thermal conductivity of saturated clayey soils. This paper presents the results of an experimental study carried out using modified consolidation tests with the needle probe method to measure thermal conductivity. Experimental consolidation tests with saturated kaolinite were performed to investigate the effect of effective stress and dry density on thermal conductivity for saturated kaolinite. In addition, thermal conductivity of soil particles were thoroughly investigated and experimental results were used to evaluate the accuracy of the models to predict thermal conductivity.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.2
• /
• pp.35-45
• /
• 2013

The void ratio is an important parameter for reflecting the soil behavior including physical property, compressibility, and relative density. The void ratio can be obtained by laboratory test with extracted soil samples. However, the specimen has a possibility to be easily disturbed due to the stress relief when extracting, vibration during transportation, and error in experimental process. Thus, the theoretical equations have been suggested for obtaing the void ratio based on the elastic wave velocities. The objective of this paper is to verify the accuracy of the proposed analytical solution through the error norm. The paper covers the theoretical methods of Wood, Gassmann and Foti. The elastic wave velocity is determined by the Field Velocity Probe in the southern part of Korean Peninsular. And the rest parameters are assumed based on the reference values. The Gassmann method shows the high reliability on determining the void ratio. The error norm is also analyzed as substitution of every parameter. The results show every equation has various characteristics. Thus, this paper may be widely applied for obtaining the void ratio according to the field condition.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.3C
• /
• pp.179-186
• /
• 2008

Pressuremeter test estimates the deformational properties of soil from the relationship between applied pressure and the displacement of cavity wall. It is general to utilize the reloading curve for the estimation of deformational properties of soil because the initial loading curve can be affected by the disturbance caused by boring. On the other hand, the instrumental resolution or the variation of measured data makes it hard to estimate the maximum shear modulus from pressuremeter test results. This study suggested the methodology estimating the maximum shear modulus from pressuremeter test directly, based on the curve fitting of reloading curve. In addition, the difference was taken into account between the stress state around the probe in reloading and that of the in-situ state. Pressuremeter tests were conducted for 15 cases using a large calibration chamber, together with a number of reference tests. The maximum shear moduli taken from suggested method were compared with those from empirical correlation and bender element test.

• The Journal of Korean Academy of Prosthodontics
• /
• v.29 no.3
• /
• pp.75-86
• /
• 1991

Ion exchange strengthening is a chemical process whereby large alkali ions(such as potassium) are substituted for smaller ions(sodium) within the surfaces of glasses and ceramics, thereby reducing the thermal expansion coefficient of this surface region, and creating beneficial state of compressive stress within the near surface region. The purpose of this study was to determine the effects of ion exchange and etching treatments on the strength of some dental porcelains. Two feldspathic dental porcelains(Vitadur-N, G-Cera) were used in this study. A commercial ion exchange paste and etching gel containing 8% hydrofluoric acid were used for surface conditioning. Transverse strength was measured using a universal testing machine and the technique of EPMA(electron probe micro analysis) was used to access the potassium contents. The results were as follows: 1. Improvement in strength was only obtained by treating the surface placed in tension. 2. No changes in the dimensions of the treated specimens were detected when samples were measured with a micrometer. 3. There was significant increase in transverse strength of G-Cera IV group treated with etching and ion exchange, compared with G-Cera II group only treated with ion exchange. 4. From the results of EPMA test, increase in potassium contents was observed on the surface treated with ion exchange paste.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.12
• /
• pp.9-17
• /
• 2006

An experimental study was carried out to examine the behavior of the unsteady boundary layer. An NACA 0012 airfoil with aspect ratio of 2.7 was set vertically in a test section, which is sinusoidally pitched about the quarter chord. The oscillating amplitude is from -6$^{\circ}$ to +6$^{\circ}$ and the mean angle of attack is 0$^{\circ}$. Surface mounted probes (Glue-on probes) were employed to measure the surface flow of the boundary layer. Measurements were made at free-stream velocities of 1.98, 2.83, and 4.03m/s, and the corresponding Reynolds numbers based on the chord length were 2.3$\times$104, 3.3$\times$104 and 4.8$\times$104, respectively. The reduced frequency is fixed as 0.1 in all cases. The results show that the surface position of minimum shear stress and of boundary layer break-down can be discerned in the Reynolds number between 2.3$\times$104 and 3.3$\times$104.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.35 no.1
• /
• pp.52-60
• /
• 2015

Nuclear power plant contain many dissimilar metal welds that connect carbon steel components with stainless steel pipes using alloy600 welding materials. Primary water stress corrosion cracks at dissimilar metal welds have been continuously reported around the world. In periodic integrity evaluations, dissimilar metal welds are examined using a generic ultrasonic testing procedure, KPD-UT-10. In this procedure, the gap between the probe and examination surface is limited to 1/32 inch (0.8mm). It is not easy to test some dissimilar metal welds in Korean plants applying ordinary technology because of their tapered shapes and irregular surface conditions. This paper introduces a method for applying a flexible phased array technology to improve the reliability of ultrasonic testing results for various shapes and surface conditions. The artificial flaws in specimens with irregular surfaces were completely detected using the flexible phased array ultrasonic technology. Therefore, it can be said that the technology is applicable to field examination.