• 전기학회논문지
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• 제59권12호
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• pp.2240-2244
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• 2010

We have studied white OLED using two types of Zn-complexes as a emitting layer. We synthesized new emissive materials $Zn(HPQ)_2$ as a yellow emitting material and $Zn(HPB)_2$ as a blue emitting material. Zn-complexes have a low molecular compound and thermal stability. The fundamental structures of the fabricated OLED was ITO / NPB (40nm) / $Zn(HPB)_2$ (30nm) / $Zn(HPQ)_2$ / LiF / Al. We varied the thickness of the $Zn(HPQ)_2$ layer 20, 30 40 nm. When the thickness of the $Zn(HPQ)_2$ layer was 20 nm, white emission was achieved. The maximum luminance was 12,000 cd/$m^2$ at a current density of 800 mA/$cm^2$. The CIE coordinates of the white emission was (0.319. 0.338) at an applied voltage of 10 V.

• International Journal of Internet, Broadcasting and Communication
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• 제12권2호
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• pp.30-36
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• 2020

We demonstrated a successful fabrication of 4" Gallium Nitride (GaN)/Diamond High Electron Mobility Transistors (HEMTs) incorporated with Inner Slot Via Hole process. We made in manufacturing technology of 4" GaN/Diamond HEMT wafers in a compound semiconductor foundry since reported [1]. Wafer thickness uniformity and wafer flatness of starting GaN/Diamond wafers have improved greatly, which contributed to improved processing yield. By optimizing Laser drilling techniques, we successfully demonstrated a through-substrate-via process, which is last hurdle in GaN/Diamond manufacturing technology. To fully exploit Diamond's superior thermal property for GaN HEMT devices, we include Aluminum Nitride (AlN) barrier in epitaxial layer structure, in addition to conventional Aluminum Gallium Nitride (AlGaN) barrier layer. The current collapse revealed very stable up to Vds = 90 V. The trapping behaviors were measured Emission Microscope (EMMI). The traps are located in interface between Silicon Nitride (SiN) passivation layer and GaN cap layer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.113-118
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• 2000

Experimental results describing the effects of blowing ratio on film cooling from two rows of holes with opposite orientation angles are presented. The inclination angle was fixed at $35^{\circ}$ and the orientation angles were set to be $45^{\circ}$ for downstream row. and $-45^{\circ}$ for upsream row. The studied blowing ratios were 0.5, 1.0 and 2.0. The boundary layer temperature distributions were measured using thermocouple at two downstream loundary layer temperature distributions were measured using thermocouple at two downstream locations. Detailed adiabatic film cooling effectiveness and heat transfer coefficient distributions were measured with TLC(Thermochromic Liquid Crystal). The adiabatic film cooling effectiveness and heat transfer coefficient distributions are discussed in connection with the injectant behaviors inferred from the boundary layer temperature distributions. Film cooling performance, represented by heat flux was calculated with the adiabatic film cooling effectiveness and heat transfer coefficient data.

• 한국표면공학회지
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• 제32권6호
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• pp.647-657
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• 1999

Due to the inherently poor adhesion strength of Cu-based leadframe/EMC (Epoxy Molding Compound) interface, popcorn cracking of thin plastic packages frequently occurs during the solder reflow process. In the present work, in order to enhance the adhesion strength of Cu-based leadframe/EMC interface, black-oxide layer was formed on the leadframe surface by chemical oxidation of leadframe, and then oxidized leadframe sheets were molded with EMC and machined to form SDCB (Sandwiched Double-Cantilever Beam) and SBN (Sandwiched Brazil-Nut) specimens. SDCB and SBN specimens were designed to measure the adhesion strength between leadframe and EMC in terms of critical energy-release rate under quasi-Mode I ($G_{IC}$ ) and mixed Mode loading ($G_{C}$ /) conditions, respectively. Results showed that black-oxide treatment of Cu-based leadframe initially introduced pebble-like X$C_2$O crystals with smooth facets on its surface, and after the full growth of $Cu_2$O layer, acicular CuO crystals were formed atop of the $Cu_2$O layer. According to the result of SDCB test, $Cu_2$O crystals on the leadframe surface did not increase ($G_{IC}$), however, acicular CuO crystals on the $Cu_2$O layer enhanced $G_{IC}$ considerably. The main reason for the adhesion improvement seems to be associated with the adhesion of CuO to EMC by mechanical interlocking mechanism. On the other hand, as the Mode II component increased, $G_{C}$ was increased, and when the phase angle was -34$^{\circ}$, crack Kinking into EMC was occured.d.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.30-32
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• 2006

The interfacial reaction and reliability of eutectic Sn-Pb and Pb-free eutectic Sn-Ag ball-grid-array (BGA) solders with an immersion Ag-plated Cu substrate were evaluated following isothermal aging at $150^{\circ}C$. During reflowing, the topmost Ag layer was dissolved completely into the molten solder, leaving the Cu layer exposed to the molten solder for both solder systems. A typical scallop-type Cu-Sn intermetallic compound (IMC) layer was formed at both of the solder/Cu interfaces during reflowing. The thickness of the Cu-Sn IMCs for both solders was found to increase linearly with the square root of isothermal aging time. The growth of the $Cu_3Sn$ layer for the Sn-37Pb solder was faster than that for the Sn-3.5Ag solder, In the case of the Sn-37Pb solder, the formation of the Pb-rich layer on the Cu-Sn IMC layer retarded the growth of the $Cu_6Sn_5$ IMC layer, and thereby increased the growth rate of the $Cu_3Sn$ IMC layer. In the ball shear test conducted on the Sn-37Pb/Ag-plated Cu joint after aging for 500h, fracturing occurred at the solder/$Cu_6Sn_5$ interface. The shear failure was significantly related to the interfacial adhesion strength between the Pb-rich and $Cu_6Sn_5$ IMC layers. On the other hand, all fracturing occurred in the bulk solder for the Sn-3.5Ag/Ag-plated Cu joint, which confirmed its desirable joint reliability.

• 마이크로전자및패키징학회지
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• 제18권2호
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• pp.49-55
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• 2011

전자기기에서의 고장 중 대부분은 작동 중 발생하는 열과 충격에 기인한다. 이 열과 충격은 PCB(Printed Board) 부품의 접합부 계면에 균열을 야기 시키고, 이 균열은 금속간 화합물(Intermetallic Compound: IMC)의 형성과 밀접한 관계를 가진다. 본 연구에서는 Sn-Ag-Cu계의 Ag함량을 변화한 Sn-1.0Ag-0.5Cu와 Sn-1.2Ag-0.5Cu 및 Sn-3.0Ag-0.5Cu의 3가지 조성의 솔더로 접합한 소재를 대상으로 1000시간 까지 등온시효(Isothermal Aging) 하였다. 등온시효 동 안 솔더(Solder)의 계면에 발생하는 IMC(Intermetallic Compound) 성장이 관찰되었으며, solder 접합부의 기계적 특성은 굽힘충격 시험법을 이용하여 평가되었다. 그 결과 시효처리 전에는 Ag 함량이 낮은 solder의 굽힘충격 특성이 우수하게 나타났으나, 시효처리 후에는 반대의 결과를 나타내었다. 이 결과는 IMC layer 주변에 생성된 미세한 $Ag_3Sn$ 및 조대한 $Cu_6Sn_5$와 관련되어, 미세한 $Ag_3Sn$이 충격을 완화한 것으로 나타나 이에 따라 굽힘충격 특성에 차이가 나타남을 알 수 있었다.

• 한국재료학회지
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• 제3권6호
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• pp.668-677
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• 1993

Cu-P계, 4종의 Cu-P-Pn계 및 3종의 Cu-P-Sn-Ag계 용가재를 사용해 Ar분위기 하에서 1003 및 1033K로 1.2Ks동안 노브레이징한 ST304, STS430 및 저탄소강과 동 접합체들을 전단시험 및 조직시험하였다. 계면에서의 미세조직은 제 종류 즉 첫째,균열을 포함하는 반응층 둘째, 분산층 세째, 균열을 포함하는 반응층과 분산층으로 분류된다. 분산층만이 존재할때 40-60MPa 이상의 상대적으로 높은 전단강도가 얻어지며, 동모재파단을 일으킨다. 이 반응층이 형성되었을때는 반드시 균열이 형성되며, 낮은 전단강도를 나타내고 접합부파단을일으킨다. 이 반응층은 Fe-P계의 화합물이다. 이러한 미소조직 및 강도 경향은 용가재내 Sn의 존재 및 모재내 Ni(또한 Cr)의 존재 유무에 따라 변화한다.

• 한국표면공학회지
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• 제40권1호
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• pp.23-31
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• 2007

The objective of this study is to investigate the effect of Al addition on the reaction behavior of cobalt with molten zinc. Pure cobalt specimen was immersion tested in the three kinds of molten zinc (pure, 0.12%Al added and 0.24%Al added) baths at $460^{\circ}C,\;490^{\circ}C\;and\;520^{\circ}C$. For the understanding of degradation processes, specimens were analyzed with scanning electron microscope (SEM) and energy dispersive spectrum (EDS), and electrochemical stripping method. When 0.12% and 0.24% Al was added in molten zinc baths, three intermetallic compounds layers of ${\gamma},\;{\gamma}_1,\;and\;{\gamma}_2$ were formed on the Co matrix and ${\beta}_1$ layer was not formed between the Co matrix and the ${\gamma}$ layer. Particles of CoAl intermetallic compound were formed at the interface between the ${\gamma}_2$ layer and zinc melt and they did not adhere to the Co-Zn intermetallic layer. Weight loss of the Co specimen increased as Al content in the molten zinc increased and the relationship of weight loss vs. immersion time followed parabolic rate law. Rate controlling process for the reaction rate of Co with Al added molten zinc was analyzed as the diffusion process of Al atom through a boundary layer between the ${\gamma}_2$ layer and the Al added zinc melt.

• 마이크로전자및패키징학회지
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• 제11권3호
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• pp.37-45
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• 2004

무전해 Ni(P)는 솔더링 특성과 부식저항성이 우수하고 표면 거칠기가 적으며 원하는 금속 상에 선택적으로 도금이 가능하여 전자패키지에서 반도체칩과 기판의 표면 금속층으로 촉 넓게 사용되고 있다. 그러나 솔더와의 반응 중 금속간 화합물의 spalling과 솔더 조인트에서의 취성파괴 문제가 성공적인 적용의 걸림돌이 되어 왔다. 본 연구에서는 각각 조성이 다른 세가지 Ni(P)막 (4.6,9, and $13 wt.\%$ P)을 사용하곡 솔더와의 반응시 무전해 Ni(P)막의 미세구조 및 상 변화와 금속간화합물의 spatting 거동을 면밀히 조사하였다. $Ni_3Sn_4$ 화합물 아래로 침투한 Sn과 P-rich layer ($Ni_3P$)와의 반응에 의해 $Ni_3SnP$ 층이 형성되며 $Ni_3SnP$ 층이 성장함에 따라 $Ni_3Sn_4$가 spalling됨이 관찰되었다. Spalling 후에는 Ni(P)막이 용융된 솔더와 직접 접촉하게 되어 Ni(P)막의 결정화가 가속화되고 $Ni_3P$상이 $Ni_2P$상으로 변태되었다. 또한 이러한 결정화 과정 중 Ni(P)막의 부피가 감소됨에 따라서 인장응력이 발생하여 막 내부에 크랙이 발생하였다.

• 대한금속재료학회지
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• 제50권4호
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• pp.316-323
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• 2012

The aim of this study is to investigate the effect of post heat treatment on bonding properties of roll cladded Ti/MS/Ti materials. First grade Ti sheets and SPCC mild steel sheets were prepared and then Ti/MS/Ti clad materials were fabricated by a cold rolling and post heat treatment process. Microstructure and point analysis of the Ti/MS interfaces were performed using the SEM and EDX Analyser. Diffusion bonding was observed at the interfaces of Ti/MS. The thickness of the diffusion layer increased with post heat treatment temperature and the diffusion layer was verified as having $({\epsilon}+{\zeta})+({\zeta}+{\beta}-Ti)$ intermetallic compounds at $700^{\circ}C$ and an $({\zeta}+{\beta}-Ti)$ intermetallic compound at $800^{\circ}C$, respectively. The micro Knoop hardness of mild steel decreased with post heat treatment temperature; however, those of Ti decreased at a range of $500{\sim}600^{\circ}C$ and showed a uniform value until $800^{\circ}C$ and then increased rapidly up to $900^{\circ}C$. The micro Knoop hardness value of the diffusion layer increased up to $700^{\circ}C$ and then saturated with post heat treatment. A T-type peel test was used to estimate the bonding forces of Ti/Mild steel interfaces. The bonding forces decreased up to $800^{\circ}C$ and then increased slightly with post heat treatment. The optimized temperature ranges for post heat treatment were $500{\sim}600^{\circ}C$ to obtain the proper formability for an additional plastic deformation process.