• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.361-365
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• 2022

Advanced packaging demands are driven by the need for dense integration systems. Consequently, stacked packaging technology has been proposed instead of reducing the ultra-fine patterns to secure economic feasibility. This study proposed an effective packaging process technology for semiconductor devices using a 9-inch dicing die attach film (DDAF), wherein the die attach and dicing films were combined. The process involved three steps: tape lamination, dicing, and bonding. Following the grinding of a silicon wafer, the tape lamination process was conducted, and the DDAF was arranged. Subsequently, a silicon wafer attached to the DDAF was separated into dies employing a blade dicing process with a two-step cut. Thereafter, one separated die was bonded with the other die as a substrate at 130 ℃ for 2 s under a pressure of 2 kgf and the chip was hardened at 120 ℃ for 30 min under a pressure of 10 kPa to remove air bubbles within the DAF. Finally, a curing process was conducted at 175 ℃ for 2 h at atmospheric pressure. Upon completing the manufacturing processes, external inspections, cross-sectional analyses, and thermal stability evaluations were conducted to confirm the optimality of the proposed technology for application of the DDAF. In particular, the shear strength test was evaluated to obtain an average of 9,905 Pa from 17 samples. Consequently, a 3D integration packaging process using DDAF is expected to be utilized as an advanced packaging technology with high reliability.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.258-258
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• 2014

Spark discharge in water generates shockwaves which have been utilized to generate mechanical actuation for potential use in pumping application. Discharge pulses of several microseconds generate shockwaves and vapor bubbles which subsequently displace the water for a period of milliseconds. Through the use of a sealed discharge chamber and metal bellow spring, the fluid motion can be used create an oscillating linear actuator. Continuous actuation of the bellow has been demonstrated through the use of high frequency spark discharge. Discharge in water forms a region of high electric field around the electrode tip which leads to the creation of a thermal plasma channel. This process produces fast thermal expansion, vapor and bubble generation, and a subsequent shockwave in the water which creates physical displacement of the water [1]. Previous work was been conducted to utilize the shockwave effect of spark discharge in water for the inactivation of bacteria, removal of mineral fouling, and the formation of sheet metal [2-4]. Pulses ranging from 25 to 40 kV and 600 to 900 A are generated inside of the chamber and the bellow motion is captured using a slow motion video camera. The maximum displacements measured are from 0.7 to 1.2 mm and show that there is a correlation between discharge energy input to the water and the displacement that is generated. Subsequent oscillations of the bellow are created by the spring force of the bellow and vapor in the chamber. Using microsecond shutter speed ICCD imaging, the development of the discharge bubble and spark can be observed and measured.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.16-16
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• 2011

Plasmas in saline solutions receive considerable attention in recent years. How the operating parameters influence the plasma characteristics and how the electrode erosion occurs have been topics that require further study. In the first part of this talk, the effect of the frequency on the plasmas characteristics in saline solution driven by 50~1000 Hz AC power will be presented. Two distinct modes, namely bubble and jetting modes, are identified. The bubble mode occurs under low frequencies. In this mode, one mm-sized bubble is tightly attached to the electrode tip and oscillates with the applied voltage. With an increase in the frequency, it shows the jetting mode, in which many smaller bubbles are continuous formed and jetted away from the electrode surface. Multiple mechanisms that are potentially responsible to such a change in bubble dynamics have been proposed and the dominant mechanism is identified. From the Stark broadening of the hydrogen optical emission line, electron densities in both modes are estimated. It shows clearly that the driving frequency greatly influences the bubble dynamics, which in turn alters the plasma behavior. In the second part, the study of the erosion of a tungsten electrode immersed in saline solution under conditions suitable for bio-medical applications is presented. The electrode is immersed in 0.1 M saline solution and is positively or negatively biased using a DC power source up to 600 V. It is identified that when the electrode is positively biased, erosion by the surface electrolytic oxidation is the dominant mechanism with an applied voltage below 150 V. An increase in the applied voltage leads to the formation of the plasma and the damage by the plasma and the thermal effect becomes more prominent. The formation of the gas film at the electrode surface leads to the formation of the plasma and hinders the electrolytic erosion. In the negatively-biased electrode, no electrolytic oxidation is seen and the damage is mostly likely due to the plasma erosion and the thermal effect.

• Applied Chemistry for Engineering
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• v.27 no.6
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• pp.577-582
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• 2016

In this study, we compared and analyzed the flame retardancy and mechanical properties of three different rigid polyurethane foams (RPUF) containing noble non-halogen phosphorus flame retardant (BHP-RPUF) or halogen-phosphorus flame retardant (TCPP-RPUF) or no flame retardant material (Pure-RPUF). The noble phosphorus-based flame retardant, bis(3-(3-hydroxypropoxy)propyl) phenyl phosphate (BHP), was synthesized by the reaction between disodium phenyl phosphate and 3-chloro-1-propanol. Through universal testing machine (UTM) experiments, the compressive strength of BHP-RPUF was similar to that of TCPP-RPUF. From the result of foam morphology analysis, it was confirmed that BHP-RPUF has the lowest thermal conductivity of $0.023W/m{\cdot}K$. We also measured the size of air bubbles using reaction velocity and SEM, and analyzed how they affect the thermal conductivity. In addition, the heat-resisting property was investigated through TGA analysis. The limited oxygen index (LOI) test confirmed that BHP had the ability to increase the flame retardancy of RPUF.

• Journal of the Korea Institute of Building Construction
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• v.20 no.5
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• pp.417-423
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• 2020

In order to reduce cooling and heating, which is 40% of the energy consumption of buildings, it is important to improve the insulation of the skin. In order to improve the existing insulation, research is being conducted to apply a vacuum insulation panel(VIP) to buildings. However, VIP cannot be repaired, so we considered the metal vacuum insulation panel. Since the core of the metal vacuum pressure and have low thermal conductivity, foam concrete is adopted. However, preliminary experiments confirmed that the time to reach 0.001torr differs depending on the amount and nature of the bubbles. This effect is determined by the type of foaming agent and the density of the bubble slurry, the vacuum delivery time is determined to be the optimum foam concrete conditions are necessary. Therfore, this study aims to present basic data applicable to core materials by measuring vacuum delivery time and thermal conductivity change according to the foaming agent type and foam slurry density of foam large concrete which is core material of metal vacuum insulation panel. Experimental results and analysis show that compressive strength can be used regardless of the type of foam, In terms of thermal conductivity, it is stable to use vegetable foaming agents at 0.9g/㎤ or less. In terms of the vacuum delivery time, the foaming agent appeared similar regardless of the type of foaming agent, but it is considered suitable to use vegetable foaming agent based on compressive strength and thermal conductivity.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.571-578
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• 2017

Bubbles are generated by the boiling of the cooling water when an accident occurs in the reactor and then in order to measure the void fraction, the Optical Fiber Probe(OFP) and optical camera are used in thermal hydraulic safety research. However, such an optical method is not suitable for measuring the void fraction in a $17{\times}17$ array of fuel rods due to the geometrical limitations. This study was conducted as a preliminary study using x-ray system and various phantoms before applying to rod bundles. Through radiographic and tomographic experiments, the tube voltage of the x-ray generator was 130 kVp and the tube current was 1 mA. In addition, it is possible to measure the hole of 1mm in size visually through the bubble resolution phantom, and it is confirmed that the contrast is relatively decreased in the inside of the freon in the case of the contrast evaluation using the road phantom. However, we could obtain good image without distortion when reconstructing the image. Bubble generation phantom experiments were used to confirm the flow direction of the bubbles and to acquire tomography images. The image J tool was used to measure the void fraction of 18 % for a single tomography image. This study has carried out previous researches for the measurement of the bubble rate around the nuclear fuel and could be used as a basic research for continuous research.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.847-858
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• 2016

An overview is given on the work of the Laboratory of Nuclear Energy Systems at ETH, Zurich (ETHZ) and of the Laboratory of Thermal Hydraulics at Paul Scherrer Institute (PSI), Switzerland on tight-lattice bundles. Two-phase flow in subchannels of a tight triangular lattice was studied experimentally and by computational fluid dynamics simulations. Two adiabatic facilities were used: (1) a vertical channel modeling a pair of neighboring sub-channels; and (2) an arrangement of four subchannels with one subchannel in the center. The first geometry was equipped with two electrical film sensors placed on opposing rod surfaces forming the subchannel gap. They recorded 2D liquid film thickness distributions on a domain of $16{\times}64$ measuring points each, with a time resolution of 10 kHz. In the bubbly and slug flow regime, information on the bubble size, shape, and velocity and the residual liquid film thickness underneath the bubbles were obtained. The second channel was investigated using cold neutron tomography, which allowed the measurement of average liquid film profiles showing the effect of spacer grids with vanes. The results were reproduced by large eddy simulation + volume of fluid. In the outlook, a novel nonadiabatic subchannel experiment is introduced that can be driven to steady-state dryout. A refrigerant is heated by a heavy water circuit, which allows the application of cold neutron tomography.

• Nuclear Engineering and Technology
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• v.44 no.4
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• pp.429-436
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• 2012

Critical heat flux (CHF) is the thermal limit of a phenomenon in which a phase change occurs during heating (such as bubbles forming on a metal surface used to heat water), which suddenly decreases the heat transfer efficiency, thus causing localized overheating of the heating surface. The enhancement of CHF can increase the safety margins and allow operation at higher heat fluxes; thus, it can increase the economy. A very interesting characteristic of nanofluids is their ability to significantly enhance the CHF. Nanofluids are nanotechnology-based colloidal dispersions engineered through the stable suspension of nanoparticles. All experiments were performed in round tubes with an inner diameter of 0.01041 m and a length of 0.5 m under low pressure and low flow (LPLF) conditions at a fixed inlet temperature using water, 0.01 vol.% $Al_2O_3$/water nanofluid, and SiC/water nanofluid. It was found that the CHF of the nanofluids was enhanced and the CHF of the SiC/water nanofluid was more enhanced than that of the $Al_2O_3$/water nanofluid.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.9
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• pp.423-429
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• 2002

RuOx thin films were fabricated by the method of liquid delivery MOCVD using Ru(C$_{8}$ $H_{13}$ $O_2$)$_3$ as the precursor and their thermal effects and conductivity were investigated. Ru films deposited at 25$0^{\circ}C$ were annealed at $650^{\circ}C$ for 1min with Ar, $N_2$ or N $H_3$ ambient. The changes of the micro-structure, the surface morphology and the electrical resistivity of the Ru films after annealing were studied. Ar gas was more effective than $N_2$ and N $H_3$ gases as an ambient gas for the post annealing of the Ru films, because of smaller resistivity and denser grains. The X-ray diffraction and X-ray photoelectron spectroscopy results indicate that the Ru $O_2$ phase and the silicidation are not observed regardless of the ambient gases. The minimum resistivity of the Ru film is found to have the value of 26.35 $\mu$Ω-cm in Ar ambient. Voids were formed at Ru/TiN interface of the Ru layer after annea1ing in $N_2$ ambient. The $N_2$ gas generated due to the oxidation of the TiN layer accumulated at the Ru/TiN interface, forming bubbles; consequently, the stacked film may peel off the Ru/TiN interface.e.

• Journal of Power System Engineering
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• v.18 no.4
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• pp.23-28
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• 2014

In order to increase the performance of conventional hot water floor heating system, the bubble jet loop heat pipe for the system was developed. This experiment was conducted under next conditions : Working fluid was R-134a, charging ratio was 50%. A temperature of hot water, room temperature and flow rate were $60^{\circ}C$, $15^{\circ}C$ and 0.5~1.5 kg/min, respectively. The experimental results, show that bubble jet loop heat pipe had a high effective thermal conductivity of $4714kW/m^{\circ}C$ and a sufficient heat flux of $73W/m^2$ to heat the floor to $35^{\circ}C$ in case of the 1.5 kg/min of flow rate. So the bubble jet loop heat pipe has a possibility for appling of the floor heating system. Additionally, the visualization of bubble jet loop heat pipe was performed to understand the operating principle. Bubbles made by the narrow gap between inner tube and outer tube of evaporating part generate pulsation at liquid surface of working fluid. The pulsation had slug flow and wavy flow. So working fluid circulates in the bubble jet loop heat pipe as two phase flow pattern. And large amount of heat is transferred by the latent heat from evaporating part to condensing part.