• Nuclear Engineering and Technology
• /
• v.53 no.10
• /
• pp.3151-3157
• /
• 2021

Copper is an important structural material in various nuclear energy applications, therefore the correct knowledge of copper cross sections is crucial. The presented paper deals with a validation of different copper transport libraries by means of activation of selected samples. An intense ²⁵²Cf(sf) source with a reference neutron spectrum was used as a neutron source. After irradiation, the samples were measured using a high purity germanium detector and the dosimeter reaction rates were inferred. These experimental data were compared with MCNP6 calculations using CENDL-3.1, JENDL-4.0, ENDF/B-VII.1, ENDF/B-VIII.0, JEFF-3.2 and JEFF-3.3 evaluated Cu transport libraries. The experiment specifically focuses on ⁵⁸Ni(n,p)⁵⁸Co, ⁹³Nb(n,2n)^92mNb, ¹⁹⁷Au(n,g)¹⁹⁸Au and ⁵⁵Mn(n,g)⁵⁶Mn dosimetry reactions. Evaluated activation cross sections of these dosimetric reactions were taken from the IRDFF-II library. The best library performance depends on the energy region of interest.

• Journal of the Korean institute of surface engineering
• /
• v.46 no.4
• /
• pp.158-161
• /
• 2013

Recently, the weight reduction and miniaturization of the electronics have placed great emphasis. The miniaturization of PCB (Printed Circuit Board) as main component among the electronic components has also become progressed. The use of acid copper plating process for Via-Filling effectively forms interlayer connection in build-up PCBs with high-density interconnections. However, in the case of copper-via filled in a bath, which is greatly dependent on the effects of additives. This paper discusses effects of Cl ion on the filling of PCB vias with electrodeposited copper based on both electrochemical experiment and practical observation of cross sections of vias.

• Korean Journal of Materials Research
• /
• v.27 no.4
• /
• pp.221-228
• /
• 2017

Various morphologies of copper oxide (CuO) have been considered to be of both fundamental and practical importance in the field of electronic materials. In this study, using Cu ($0.1{\mu}m$ and $7{\mu}m$) particles, flake-type CuO particles were grown via a wet oxidation method for 5min and 60min at $75^{\circ}C$. Using the prepared CuO, AlN, and silicone base as reagents, thermal interface material (TIM) compounds were synthesized using a high speed paste mixer. The properties of the thermal compounds prepared using the CuO particles were observed by thermal conductivity and breakdown voltage measurement. Most importantly, the volume of thermal compounds created using CuO particles grown from $0.1{\mu}m$ Cu particles increased by 192.5 % and 125 % depending on the growth time. The composition of CuO was confirmed by X-ray diffraction (XRD) analysis; cross sections of the grown CuO particles were observed using focused ion beam (FIB), field emission scanning electron microscopy (FE-SEM), and energy dispersive analysis by X-ray (EDAX). In addition, the thermal compound dispersion of the Cu and Al elements were observed by X-ray elemental mapping.

• Journal of Radiation Protection and Research
• /
• v.26 no.3
• /
• pp.327-331
• /
• 2001

The Pohang Neutron Facility based on an electron linac was constructed in order to construct the infrastructure for nuclear data production in Korea. It consists of a 100-MeV electron linac, a water-cooled Ta target, and an 11-m time-of-flight path. We measured the time-of-flight path length, the neutron energy spectra for different water levels inside the moderator, and the neutron total cross sections of polyethylene and copper by the transmission method.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.3
• /
• pp.341-346
• /
• 2010

The effect of specimen geometry on the bending and tensile strengths of dissimilar joints ($\beta-Si_3N_4/S45C$) with copper interlayers was evaluated. The average bending strength of specimens with circular cross sections was higher than that of specimens with rectangular cross sections. The crack initiation stress ($\sigma_i$) was successfully determined by the acoustic emission (AE) method and was approximately 60~80% of the bending strength. The residual stresses near the interfaces on the ceramic side were measured by X-ray diffraction before conducting the bending test. The bending strength and the crack initiation stress decreased with an increase in the residual stresses. The effect of the bending strain component was evaluated by the tensile testing; the tensile strength decreased with an increase in the bending strain component and was approximately 80% of the bending strength.

• Journal of the Microelectronics and Packaging Society
• /
• v.22 no.1
• /
• pp.51-54
• /
• 2015

An electro-plating technology on a cured isotropic conductive pattern with a hybrid Cu paste composed of resin matrix, copper, and solder powders has been developed. In a conventional technology, Ag paste was used to perform a conductive pattern on a PCB or silicon substrate. From previous research, the electrical conductive mechanism and principle of the hybrid Cu paste were concisely investigated. The isotropic conductive pattern on the PCB substrate was performed using screen-printing technology. The optimum electro-plating condition was experimentally determined by processing parameters such as the metal content of the hybrid Cu paste, applied current density, and time for the electroplating in the plating bath. The surfaces and cross-sections were observed using optical and SEM photographs. In conclusion, the optimized processing conditions for Cu electro-plating technology on the conductive pattern were a current density of $40mA/cm^2$ and a plating time of 20min on the hybrid Cu paste with a metal content of 44 vol.%. More details of the mechanical properties and processing conditions will be investigated in further research.

• Journal of Welding and Joining
• /
• v.33 no.3
• /
• pp.47-53
• /
• 2015

By the trends of electronic package to be more integrative, the fine Cu trace pitch of organic PCB is required to be a robust design. In this study, the short circuit failure mechanism of PCB with a Cl element under the Temperature humidity bias test ($85^{\circ}C$/85%RH/3.5V) was examined by micro-structural study. A focused ion beam (FIB) and an electron probe micro analysis (EPMA) were used to polish the cross sections to reveal details of the microstructure of the failure mode. It is found that $CuCl_x$ were formed and grown on Cu trace during the $170^{\circ}C$/3hrs and that $CuCl_x$ was decomposed into Cu dendrite and $Cl_2$ gas during the $85^{\circ}C$/85%RH/3.5V. It is suggested that Cu dendrites formed on Cu trace lead to a short circuit failure between a pair of Cu traces.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.2
• /
• pp.75-80
• /
• 2008

The fabrication of complex three-dimensional electrodes for micro electrical discharge machining (micro-EDM) is an important issue in the field of micromachining Localized electrochemical deposition (LECD) is a simple and inexpensive technique for fabricating micro-EDM electrodes. This study presents a new process for manufacturing electrodes with complex cross-sections using masks of different shapes, In this process, a non-conductive mask is placed between an anode and cathode that are immersed in a plating solution of acidified copper sulfate. The LECD is achieved by applying a pulsed voltage between the anode and cathode, which are separated by a small distance. In this setup, the cathode is placed above the anode and the mask, so that the deposited electrode can be used directly for EDM without changing the tool orientation. We found that the microstructure of the deposited electrode is influenced by the concentration of the plating solution and organic additives. Moreover, the values of the voltage, frequency, and duty cycle of the pulsed input have significant effects on the microstructure of the fabricated electrode. Finally, the optimum values of the voltage, frequency, and duty cycle were determined for the most effective fabrication of complex-shaped electrodes.

• Journal of the Microelectronics and Packaging Society
• /
• v.22 no.1
• /
• pp.43-49
• /
• 2015

By the trends of electronic package to be smaller, thinner and more integrative, organic printed circuit board is required to be finer Cu trace pitch. This paper reports on a study of failure mechanism for PCB with fine Cu trace pitch using biased HAST. In weibull analysis of the biased HAST lifetime, it is found that the acceleration factor (AF) of between $135^{\circ}C/90%RH/3.3V$ and $130^{\circ}C/85%RH/3.3V$ is 2.079. A focused ion beam (FIB) was used to polish the cross sections to reveal details of the microstructure of the failure mode. It is found that $Cu_xO/Cu(OH)_2$ colloids and Cu dendrites were formed at anode (+) and at cathode (-), respectively. Thus, this gives the evidence that Cu dendrites formed at cathode by $Cu^{2+}$ ion migration lead to a short failure between a pair of Cu nets.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.29 no.8
• /
• pp.408-418
• /
• 2017

Supercritical carbon dioxide ($sCO_2$) power system is emerging technology because of its high cycle efficiency and compactness. Meanwhile, PCHE (Printed Circuit Heat Exchanger) is gaining attention in $sCO_2$ power system technology because PCHE with high pressure-resistance and larger heat transfer surface per unit volume is fundamentally needed. Thermo-fluidic characteristics of $sCO_2$ in the micro channel of PCHE should be investigated. In this study, heat transfer characteristics of $sCO_2$ of various inlet conditions and cross-sectional shapes of single micro channel were investigated experimentally. Experiment was conducted at supercritical state of higher than critical temperature and pressure. Test sections were made of copper and hydraulic diameter was 1 mm. Convective heat transfer coefficients were measured according to each interval of the channel and pressure drop was also measured. Convective heat transfer coefficients from experimental data were compared with existing correlation. In this study, using measured data, a new empirical correlation to predict near critical region heat transfer coefficient is developed and suggested. Test results of single channel will be used for design of PCHE.