• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.1-8
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• 2010

Natural convection heat transfer rates in a vertical pipe were measured for $Gr_H$ number from 2.1x$10^6$ to 1.2x$10^9$. Using the analogy concept, heat transfer experiments were replaced by mass transfer experiments. A cupric acid - copper sulfate ($H_2SO_4-CuSO_4$) electroplating system was adopted as the mass transfer system and the mass transfer rates were measured. Comparison of the results with the existing laminar and turbulent natural convection heat transfer correlations on a vertical plate showed very good agreements except for the high $Gr_H$ case, where the boundary layer inside the vertical pipe interferes. The agreements showed the usefulness of the analogy experiment method. Using 3 different anode size and 6 different geometrical configurations, the effects of the anode size and position were explored. As expected, the anode size and position do not affect the limiting currents for most cases. These results will be used as the experimental background for the positioning and sizing of the anodes for a more complex experiment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.417-424
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• 2011

Natural convection heat transfer experiments from two parallel horizontal cylinders were performed varying the Pitch-to-Diameter ratio (P/D) of 1.02-9 at Sc of 2,014 to 8,334 and $Ra_D$ of $1.5{\times}10^8$ to $4.5{\times}10^{10}$. Mass transfer experiments that are analogous to the heat transfer experiments were performed using copper electroplating system. In all cases, the measured heat transfer rates for the lower cylinder agreed well with the existing heat transfer correlations developed from a single cylinder. For laminar flows, the measured heat transfer rates of the upper cylinder were less than those of the lower cylinder at P/D less than about 1.5. However, as the P/D increased, the heat transfer rates of the upper cylinder increased. For turbulent flows, the heat transfer rates of the upper cylinder were considerably similar to those of the lower cylinder when the P/D is approximately unity. In contrast, as the P/D increased, the heat transfer rates of the upper cylinder were always higher than those of the lower cylinder.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.79-84
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• 2010

Formation of TSV (Through-Si-Via) with an Au seed layer and Cu filling to the via, simplification of bumping process for three dimensional stacking of Si dice were investigated. In order to produce the via holes, the Si wafer was etched by a DRIE (Deep Reactive Ion Etching) process using $SF_6$ and $C_4F_8$ plasmas alternately. The vias were 40 ${\mu}m$ in diameter, 80 ${\mu}m$ in depth, and were produced by etching for 1.92 ks. On the via side wall, a dielectric layer of $SiO_2$ was formed by thermal oxidation, and an adhesion layer of Ti, and a seed layer of Au were applied by sputtering. Electroplating with pulsed DC was applied to fill the via holes with Cu. The plating condition was at a forward pulse current density of 1000 mA/$dm^2$ for 5 s and a reverse pulse current density of 190 mA/$dm^2$ for 25 s. By using these parameters, sound Cu filling was obtained in the vias with a total plating time of 57.6 ks. Sn bumping was performed on the Cu plugs without lithography process. The bumps were produced on the Si die successfully by the simplified process without serious defect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.481-489
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• 2010

Experiments on laminar mixed convection in a vertical pipe were performed for the Re range 1,000-3,000, the $Gr_H$ range $10^5-10^8$, the Pr range 2,000-7,000, and aspect ratio range 1-7. Using the analogy concept, heat transfer systems were simulated by mass transfer systems. A cupric acid.copper sulfate electroplating system was adopted as the mass transfer system, and the mass transfer rates were measured. The measured Nu values were far greater than those previously reported because of the large value of pr in this experiment. As the aspect ratio in this study was not sufficiently large for the flow to be fully developed, the test results were similar to those for mixed convection on a vertical plate rather than that inside a long vertical pipe. It was concluded that the behavior of laminar mixed convection of a developing flow in a vertical pipe at a low aspect ratio and low $Gr_H$ is similar to that of laminar mixed convection in the vertical plate. As the aspect ratio and $Gr_H$ increase, the laminar mixed convection phenomena becomes similar to that observed in a fully developed flow in the vertical pipe.

• Journal of Energy Engineering
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• v.21 no.3
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• pp.254-264
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• 2012

Rayleigh-Benard natural convection experiments were carried out as the preliminary experiment to simulate the natural convection of the core melt at the severe accident conditions. This work focused on the influences of plate separation distance(s), the existence of the side walls and crust geometries of upper and lower plates. Based upon the analogy concept, a cupric acid-copper sulfate electroplating system($H_2SO_4-CuSO_4$) was employed as the mass transfer system and measurements were made for $Ra_s$ ranging from $1.06{\times}10^7$ to $2.91{\times}10^{10}$. The test results measured for a single horizontal plate were in good agreement with the correlation reported by McAdams and those for two horizontal plates showed the similar trend to the existing Rayleigh-Benard heat transfer correlations developed by Dropkin and Somerscales, Globe and Dropkin. The measured heat transfer rate decreased with the increasing separation distance between the two plates and became similar to those for a single horizontal plate. Fin arrays mounted on both upper and lower plates enhanced the heat transfer rates. For all cases, the heat transfer rates measured for open side walls are higher than those for closed ones.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.1
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• pp.71-78
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• 2023

The possibility of improving plating thickness distribution was investigated through quantitative consideration of bipolar electrodes without external power applied. By having the cathode tilted with respect to the anode, the potential distribution in the electrolyte solution adjacent to the cathode is different due to the difference in iR drop due to the path difference to the anode in each region of the cathode. The purpose of this study is to observe the bipolar characteristics in the case of an auxiliary anode for the non-uniform potential distribution of such a Hull cell. In particular, in order to evaluate the possibility of improving the non-uniform thickness distribution of the cathode by utilizing these bipolar characteristics, it was verified through experiments and simulations, and the electric potential and current density distribution around the bipolar electrode were analyzed. The electroplating in a Hull cell was performed for 75 min at a current density of 10 mA/cm², and the average thickness is about 16 ㎛. The standard deviation of the thickness was 10 ㎛ in the normal Hull cell without using the auxiliary anode, whereas it was 3.5 ㎛ in the case of using the auxiliary cathode. Simulation calculations also showed 8.9 ㎛ and 3.3 ㎛ for each condition, and it was found that the consistency between the experimental and simulation results was relatively high, and the thickness distribution could be improved through using the auxiliary anode by the bipolar phenomenon.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.225-229
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• 2009

The front metal contact is one of the most important element influences in efficiency in the silicon solar cell. First of all selective of the material and formation method is important in metal contacts. Commercial solar cells with screen-printed contacts formed by using Ag paste process is simple relatively and mass production is easy. But it suffer from a low fill factor and a high shading loss because of high contact resistance. Besides Ag paste too expensive. because of depends income. This paper applied for Ni/Cu metallization replace for paste of screen printing front metal contact. Low cost Ni and Cu metal contacts have been formed by using electroless plating and electroplating techniques to replace the screen-printed Ag contacts. Ni has been proposed as a suitable silicide for the salicidation process and is expected to replace conventional silicides. Copper is a promising material for the electrical contacts in solar cells in terms of conductivity and cost. In experiments Ni/Cu metal contact applied same grid formation of screen-printed solar cell. And it has variation of different grid spacing. It was verified that the wide spacing of grid finger could increase the series resistance also the narrow spacing of grid finger also implies a grid with a higher density of grid fingers. Through different grid spacing found alteration of efficiency.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.715-719
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• 2003

The Aerosol Deposition (AD) process will be proposed as a new fabrication technology for the integrated RF modules. $\alpha$-A1$_2$O$_3$ thick films were successfully grown on glass and Al substrates at room temperature by the AD process. Relative dielectric permittivity and loss tangent of the $Al_2$O$_3$ thick films on Al showed 9.5 and 0.005, respectively. To form microstrip lines on aerosol-deposited A1903 thick films, copper electroplating and lithography processes were employed, and the square-type cross section with sharp edges could be obtained. Low-pass LC filters with 10 GHz cutoff frequency were simulated by an electromagnetic analysis, exhibiting the validity of the AD process as a fabrication technology f3r integrated RF modules.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.249-249
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• 2015

Silver films have been of considerable interest for years due to their better performance relative to other metal films for engineering applications. A series of multi-layer silver coatings with different thickness (i.e. 0.3 um to 1.5 um) were prepared on Aluminium substrate containing copper undercoat by direct current (DC) magnetron sputtering method. For the comparative purpose, similar thickness silver coatings were prepared by electrolytic deposition method. Microstructural, morphological, and mechanical characteristics of the silver coatings were evaluated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), Surface roughness test, microhardness test and nano-scratch test. From the results, it has been elucidated that the silver films prepared by DC magnetron sputtering method has superior properties in comparison to the wet coating method. On the other hand, DC magnetron sputtering method is relatively easier, faster, eco-friendly and more productive than the electrolytic deposition method that uses several kinds of hazardous chemicals for bath formulation. Therefore, a New Work Item Proposal (NWIP) for the test methods standardization of DC magnetron sputtered silver coatings has recently been proposed via KATS, Korea and a NP ballot is being progressed within a technical committee "ISO/TC107-metallic and other inorganic coating".

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.575-579
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• 2010

The technologies of Ni/Cu plating contact is attributed to the reduced series resistance caused by a better contact conductivity of Ni with Si and the subsequent electroplating of Cu on Ni. The ability to pattern narrower grid lines for reduced light shading was combined with the lower resistance of a metal silicide contact and an improved conductivity of the plated deposit. This improves the FF (fill factor) as the series resistance is reduced. This is very much requried in the case of low concentrator solar cells in which the series resistance is one of the important and dominant parameter that affect the cell performance. A Selective emitter structure with highly dopeds regions underneath the metal contacts, is widely known to be one of the most promising high-efficiency solution in solar cell processing In this paper the formation of a selective emitter, and the nickel silicide seed layer at the front side metallization of silicon cells is considered. After generating the nickel seed layer the contacts were thickened by Cu LIP (light induced plating) and by the formation of a plated Ni/Cu two step metallization on front contacts. In fabricating a Ni/Cu plating metallization cell with a selective emitter structure it has been shown that the cell efficiency can be increased by at least 0.2%.