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방정환,이세형,신의선,김정한,이창우,Bang, Jung-Hwan,Lee, Se-Hyung,Shin, Yue-Seon,Kim, Jeong-Han,Lee, Chang-Woo 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.1
Reflow process conditions were investigated for 0402 electric parts with Sn-3.0Ag-0.5Cu solders. Circle hole shape metal mask with 100 m thickness showed excellent printability. Self alignment abilities were 71% for 1005 chips, 52% for 0603 chips, and 3% for 0402 chips. Average joining strengos were 1990 gf for 1005 chips, 867 gf for 0603 chips, and 525 gf for 0402 chips. As mis-mounting angle increased, joining strength decreased. Considering self-alignment ability, mounting angle had to be under $5^{\circ}$ and contact area of the chips had to be over 40% for Pb-free soldering process for 0402 chips.
방정환(Jeong Hwan Bang),정명수(Myong Soo Chong) 대한의료기공학회 2013 醫療氣功 Vol.13 No.1
In this study we examined the concerned literature for clinical use of Balsaminaceae plants focusing on the latest literature "zhong hua ben cao"(chinese materia medica, 1998). The findings were summarized as follows: 1. As an original plant, 27 species have been reviewed. 2. As a result of investigating oriental drug names by medicinal using part, a survey reported that the total of 22 species of oriental drug names, including 14 species of herba, 3 species of flos, 4 species of radix and rhizoma , and 1 species of semen, are being used for clinical use. 3. When we examined oriental drugs with five flavors by calculating and arranging their nature, effect, toxicity with points for conveniences sake, pungent and bitte showed 13 points, respectively, as main flavors. In drug nature, warm property of drug indicated 10 points and cold property of drug obtained 6 points. But as for other oriental drug, it is thought that we can recognize their significance. 4. With respect to efficacy, activating blood drug reached 10 kinds and wind- damp-dispelling 7 kinds, according to the examination. 5. In the examination on components and medicinal action, we examined that components are recorded in only impatiens balsamina's whole grass, flowers, root, root stems, and seeds, and Impatiens noli-tangere's whole grass. In medical action, we found out that the components are recorded in impatiens balsamina' flowers and seeds; impatiens noli-tangere's whole grass and flowers; and Impatiens textori' whole grass. 6. As a result of examining clinical prescription, the total of 84 kinds of clinical prescriptions by disease nature were examined, of which the prescription of Impatiens balsamina showed 19 cases in total, which was remarkable.
방정환(Jung-Hwan Bang),유동열(Dong-Yurl Yu),고용호(Young-Ho Ko),윤정원(Jeong-Won Yoon),이창우(Chang-Woo Lee) 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.1
Automotive today has been transforming to an electronic product by adopting a lot of convenience and safety features, suggesting that joining materials and their mechanical reliabilities are getting more important. In this study, a Sn-Cu-Cr-Ca solder composition having a high melting temperature (>230℃) was fabricated and its joint properties and reliability was investigated with an aim to evaluate the suitability as a joining material for electronics of engine room. Furthermore, mechanical properties change under complex environment were compared with several existing solder compositions. As a result of contact angle measurement, favorable spreadability of 84% was shown and the average shear strength manufactured with corresponding composition solder paste was 1.9kg/mm². Also, thermo-mechanical reliability by thermal shock and vibration test was compared with that of the representative high temperature solder materials such as Sn-3.5Ag, Sn-0.7Cu, and Sn-5.0Sb. In order to fabricate the test module, solder balls were made in joints with ENIG-finished BGA and then the BGA chip was reflowed on the OPS-finished PCB pattern. During the environmental tests, resistance change was continuously monitored and the joint strength was examined after tests. Sn-3.5Ag alloy exhibited the biggest degradation rate in resistance and shear stress and Sn-0.7Cu resulted in a relatively stable reliability against thermo-mechanical stress coming from thermal shock and vibration.
윤정원,방정환,고용호,유세훈,김준기,이창우,Yoon, Jeong-Won,Bang, Jung-Hwan,Ko, Yong-Ho,Yoo, Se-Hoon,Kim, Jun-Ki,Lee, Chang-Woo 한국마이크로전자및패키징학회 2014 마이크로전자 및 패키징학회지 Vol.21 No.4
The paper gives an overview of the concepts, basic requirements, and trends regarding packaging technologies of power modules in hybrid (HEV) and electric vehicles (EV). Power electronics is gaining more and more importance in the automotive sector due to the slow but steady progress of introducing partially or even fully electric powered vehicles. The demands for power electronic devices and systems are manifold, and concerns besides aspects such as energy efficiency, cooling and costs especially robustness and lifetime issues. Higher operation temperatures and the current density increase of new IGBT (Insulated Gate Bipolar Transistor) generations make it more and more complicated to meet the quality requirements for power electronic modules. Especially the increasing heat dissipation inside the silicon (Si) leads to maximum operation temperatures of nearly $200^{\circ}C$. As a result new packaging technologies are needed to face the demands of power modules in the future. Wide-band gap (WBG) semiconductors such as silicon carbide (SiC) or gallium nitride (GaN) have the potential to considerably enhance the energy efficiency and to reduce the weight of power electronic systems in EVs due to their improved electrical and thermal properties in comparison to Si based solutions. In this paper, we will introduce various package materials, advanced packaging technologies, heat dissipation and thermal management of advanced power modules with extended reliability for EV applications. In addition, SiC and GaN based WBG power modules will be introduced.
차체용 1.2GPa급 초고장력 TRIP강의 Weldbond 접합부의 기계적 거동
이종대,이소정,방정환,김동철,강문진,김목순,김준기,Lee, Jong-Dae,Lee, So-Jeong,Bang, Jung-Hwan,Kim, Dong-Cheol,Kang, Mun-Jin,Kim, Mok-Soon,Kim, Jun-Ki 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.5
The effect of weldbond hybrid joining process on the mechanical behavior of single lap and L-tensile joints was investigated for the newly developed 1.2GPa grade ultra high strength TRIP(transformation induced plasticity) steel. In the case of single lap shear behavior, the weldbond joint of 1.2GPa TRIP steel showed lower maximum tensile load and elongation than that of the adhesive bonding only. It was considered to be due to the reduction of real adhesion area, which was caused by the degradation of adhesive near the spot weld, and the brittle fracture behavior of the spot weld joint. In the case of L-tensile behavior, however, the maximum tensile load of the weldbond joint of 1.2GPa TRIP steel was dramatically increased and the fracture mode was change to the base metal fracture which is desirable for the spot weld joint. These synergic effect of the weldbond hybrid joining process in 1.2GPa TRIP steel was considered to be due to the stress dissipation around the spot weld joint by the presence of adhesive which resulted in the change of crack propagation path.
이종대,이소정,방정환,윤길상,김목순,김준기,Lee, Jong-Dae,Lee, So-Jeong,Bang, Jung-Hwan,Yoon, Gil-Sang,Kim, Mok-Soon,Kim, Jun-Ki 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.6
For the resistance spot welds of CR1180 and GA1180 TRIP steels, the weld quality evaluation method using the digitalized X-ray transmission imaging apparatus was investigated in comparison with the crosssectional examination method. In the case of the resistance spot welding of CR1180, three circular regions, such as WZ(white zone), GZ(grey zone) and DZ(dark zone), appeared on X-ray image and they corresponded to the diameters of indentation mark, nugget and corona bond, respectively. The variation of X-ray transmission thickness due to the thickness variation of the weld seemed to be mainly responsible for the formation of those contrasts. The X-ray image contrast formed from the variation of transmission thickness at the outer border line of DZ could also enable the inspections of the notch shape, nonuniformity of the welding pressure and spatter from its sharpness, concentricity and the normal straight line, respectively. The X-ray image of the resistance spot weld of galvannealed GA1180 TRIP steel was very similar to that of CR1180 TRIP steel except the crown shaped outer border line of DZ which was considered to be due to the melting behavior of zinc having the boiling temperature even lower than the melting temperature of steel.
CNT를 첨가한 전력케이블용 반도전 재료의 열적특성에 관한 연구
양훈,국정호,방정환,박대희,Yang, Hoon,Kook, Jeong-Ho,Bang, Jeong-Hwan,Park, Dae-Hee 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.12
In this paper, we have investigated thermal properties of semiconductive shield materials for power cables. EEA (Ethylene Ethyl Acrylate) was used for base polymer and TGA (Thermal Gravimetric Analysis) and AFM (Atomic Force Microscope) were investigated with various carbon black and CNT (carbon nanotube) contents. When CNT reinforced composites and conventional composite were investigated with TGA, we knew that thermal properties of CNT reinforced composite were better than them of conventional composite. To investigate roughness, we used AFM. Before and after aging, AFM was applied and after aging, roughness was increased. As a result, suitable CNT and CB(carbon black) content is CNT:CB=50:50.
EPR의 가속 열화에 의한 기계적 특성 및 통계적 평가
김지연,양종석,이길수,성백용,방정환,박대희,Kim, Ji-Yeon,Yang, Jong-Suk,Lee, Gil-Soo,Seong, Baek-Yong,Bang, Jeong-Hwan,Park, Dae-Hee 한국전기전자재료학회 2015 전기전자재료학회논문지 Vol.28 No.8
In this paper, EPR (ethylene propylene rubber) insulation material was accelerated degradation test at $121^{\circ}C$, $136^{\circ}C$, $151^{\circ}C$, and experiment the typical EAB (elongation at break) at mechanical characteristics analysis. It is shown that the failure-time at the point of 50% of the initial value of Elongation rate to obtain the activation energy. The failure-time was shown each 5,219 hr, 3,165 hr, and 668 hr at three temperatures. In order to derive the activation energy, Arrhenius methodology was applied. Also, we got the Arrhenius plot from three accelerated temperatures. The activation energy values got 0.98 eV from EAB test. The experimental data were evaluated for estimating the probability density, and the suitable distribution by using statistical program MINITAB. It is shown that EAB data by the acceleration thermal degradation is most suitable for the Weibull distribution.
김지연,양종석,박경흠,성백용,방정환,박대희,Kim, Ji-Yeon,Yang, Jong-Suk,Park, Kyeung-Heum,Seong, Baek-Yong,Bang, Jeong-Hwan,Park, Dae-Hee 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.1
The activation energy of a material is an important factor that significantly affects the lifetime and can be used to develop a degradation model. In this study, a thermal analysis was carried out to evaluate and collect quantitative data on the degradation of insulation materials like EPR and CSP used for nuclear power plant cables. The activation energy was determined from the relationship between log ${\beta}$ and 1/T based on the Flynn.Wall.Ozawa method, by a TGA test. The activation energy was also derived from the relationship between ln(t) and 1/T based on isothermal analysis, by an OIT test. The activation energy of EPR derived from thermal analysis was used to calculate the accelerated aging time corresponding to the number of years of use, employing the Arrhenius equation, and determine the elongation corresponding to the accelerated aging time.