Y₂O₃-BN 복합체의 미세구조 및 내플라즈마 특성

이현규,이석신,김비룡,박태언,윤영훈,Lee, Hyun-Kyu,Lee, Seokshin,Kim, Bi-Ryong,Park, Tae-Eon,Yun, Young-Hoon 한국결정성장학회 2014 한국결정성장학회지 Vol.24 No.3

$Y_2O_3$-BN 세라믹 복합체를 제작하기 위해서, 분말 입도 $3{\sim}10{\mu}m$인 $Y_2O_3$ 분말을 분산한 슬러리에 pH 조절제인 NaOH를 첨가하였으며 결합제로는 PVA, 가소제로는 PEG를, BN 분말과 혼합하고, 분무건조(spray drying)공정을 거쳐 $Y_2O_3$ 혼합 분말을 제조하였다. ${\O}14mm$ 크기의 $Y_2O_3$-BN 시편을 성형하고, $1550^{\circ}C$ 및 $1600^{\circ}C$에서 소결하여 $Y_2O_3$-BN 복합체를 제작하였다. BN 투입량과 소결온도의 변수에 따른 미세구조, 순도, 꺽임강도, 열팽창계수, 밀도, 체적저항, 내플라즈마 특성을 조사하였다. $Y_2O_3$-BN ceramic composites were fabricated from the slurries of yttria powder with average particle size of 3~10 ${\mu}m$. The slurry was fabricated by mixing PVA binder, NaOH for Ph control, PEG, BN powder and $Y_2O_3$ powder. The mixed $Y_2O_3$ powders were obtained by spray drying process from the slurry. The $Y_2O_3$-BN composite specimen was shaped in size of ${\O}14mm$ and then sintered at $1550^{\circ}C$ and $1600^{\circ}C$, respectively. The characteristics, microstructure, purities, densities, bulk resistance, thermal expansion, hardness and plasma resistance of the $Y_2O_3$-BN composites were investigated with the function of BN contents and sintering temperature.

Al-CuAl2 공정복합재료의 기계적 성질에 미치는 응고조건과 열처리의 영향

이현규,이주홍,홍종휘 ( Hyun Kyu Lee,Ju Hong Lee,Jong Hwi Hong ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.4

N/A The structure and tensile properties of the unidirectionally solidified Al-33wt.%Cu alloy have been investigated. Casted Al-33wt.%Cu alloy was unidirectionally solidified with rates (R) between 1㎝/hr and 24㎝/hr maintaining the thermal gradient(G) at solid-liquid interface, 32℃/㎝ and 21℃/㎝. The entectic struture was varied according to the growth condition(G/R radio). When G/R ratio was larger than 8.5×10³℃/㎠ /sec the lamellar structure was formed, and colony structure was formed when G/R ratio was smaller than 8.5×10³℃/㎠ /sec. The interlamellar spacing(λ) in the above alloy system was vaired with the growth rate(R) According to λ²·R=8.8 × 10^(-11)㎤ /sec relationship. The yield stress (σ0.001) and UTS for samples in the as-grown condition increased with the interlamellar spacing decrease and the values corresponding to colony structure are lower than those corresponding to amellar structure with the same lamellar spacing. The yield stress for samples in aged condition did not change with the interlamellar spacing.

전해Ni, 무전해 Ni pad에서의 Cu 함량에 따른 접합 신뢰성에 관한 연구

이현규,천명호,추용철,오금술,Lee, Hyun Kyu,Chun, Myung Ho,Chu, Yong Chul,Oh, Kum-Sool 한국마이크로전자및패키징학회 2015 마이크로전자 및 패키징학회지 Vol.22 No.3

It has been used various pad finish materials to enhance the reliability of solder joint and recently Electroless Ni Electroless Pd Immersion Gold (the following : ENEPIG) pad has been used more than others. This study is about reliability according to being used in commercial Electrolytic Ni pad and ENEPIG pad, and was observed behavior of various Cu contents. After reflow, the inter-metallic compound (IMC) between solder and pad is composed of $Cu_6Sn_5$ (Ni substituted) by using EDS, and in case of ENEPIG, between IMC and Ni layer was observed the dark layer ($Ni_3P$ layer). Additional, it could be controlled the thickness of dark layer according to Cu contents. Investigated the different fracture mode between electrolytic Ni and ENEPIG pad after drop shock test, in case of soft Ni, accelerated stress propagated along the interface between $1^{st}$ IMC and $2^{nd}$ IMC, and in case of ENEPIG pad, accelerated stress propagated along the weaken surface such as dark layer. The unstable interface exists through IMC, pad material and solder bulk by the lattice mismatch, so that the thermal and physical stress due to the continuous exterior impact is transferred to the IMC interface. Therefore, it is strongly requested to control solder morphology, IMC shape and thickness to improve the solder reliability. 솔더 조인트의 신뢰성 강화를 위해서 다양한 pad finish material이 사용되고 있으며, 최근에는 Electroless Ni Electroless Pd Immersion Gold (이하 ENEPIG) pad가 많이 사용되고 있다. 따라서, 본 연구는 상용화 되어 사용중인 Electrolytic Ni (soft Ni) pad와 최근 이슈가 되고 있는 ENEPIG pad에 대한 신뢰성 평가에 관한 것으로, 다양한 Cu 함량에 따른 거동을 관찰 하였다. Reflow 후 솔더와 pad간의 접합층은 $Cu_6Sn_5$에 Ni이 치환된 형태의 금속간 화합물로 구성되어 있었으며, ENEPIG pad의 경우, 접합층과 Ni layer 사이에 $Ni_3P$ (dark layer) layer가 관찰 되었다. 또한, Cu 함량에 따라 Dark layer의 두께를 제어할 수 있었다. 충격 낙하 시험 후, 파괴모드를 관찰한 결과 soft Ni pad와 ENEPIG pad에서 서로 다른 파괴모드가 관찰 되었으며, soft Ni의 경우, 1차 IMC와 2차 IMC 경계에서 파괴가 관찰 되었고, ENEPIG pad의 경우, dark layer에서 파괴가 관찰 되었다. IMC와 pad material, bulk 솔더와의 lattice mismatch에 의해 불안정한 계면이 존재하며, 이는 연속적인 외부 충격에 의해 가해진 열적, 물리적 스트레스를 IMC 계면으로 전송하기 때문에, 솔더의 신뢰성 향상을 위해서는 솔더 벌크의 제어와 IMC의 두께 및 형상의 제어는 필요하다.

기생소자에 의한 소형 평면 맴돌이형 모노폴 안테나

이현규,이택경,장원호,강연덕,Lee Hyun-Kyu,Lee Taek-Kyung,Jang Won-Ho,Kang Yeon-Duk 한국전자파학회 2005 한국전자파학회논문지 Vol.16 No.6

본 논문에서는 기생소자를 사용하여 소형화된 평면형 맴돌이형 모노폴 안테나를 제안한다. 이 기생소자는 십자형태의 스트립과 L자 형태로 구부러진 스트립으로 구성되며 방사체가 있는 기판의 반대면에 인쇄된다. 이 기생소자를 적용시 맴돌이형 모노폴 안테나는 기생소자가 없는 모노폴 안테나에 비해 $32\%$의 안테나크기 축소 효과를 가진다. 또한 이 안테나의 수평 단면 복사 패턴은 일반적인 모노폴 안테나에서 요구되는 등방향성을 유지한다. 제안된 안테나는 TV 채널 12번을 사용하는 지상파 digital multimedia broadcasting(DMB) 수신기용으로 설계되었다. In this paper, a small-sized planar square-spiral monopole antenna is proposed by using parasitic elements. The Parasitic element is composed of a crossed strip and additional right-angle folded(L-type) stirps. And these parasitic elements are printed on a substrate which is the opposite side of a radiation element . When the parasitic elements are used, the size of the square-spiral monopole antenna is reduced by $32\%$ for the same operating frequency compared to the antenna without parasitic elements. The radiation pattern of the proposed antenna is nearly omni-directional in azimuth. The designed antenna can be used in the application of channel 12 digital mulimedia broadcasting(DMB) handset.

Y₂O₃ 세라믹스의 미세구조 및 플라즈마 저항성

이현규,이석신,김비룡,박태언,윤영훈,Lee, Hyun-Kyu,Lee, Seokshin,Kim, Bi-Ryong,Park, Tae-Eon,Yun, Young-Hoon 한국결정성장학회 2014 한국결정성장학회지 Vol.24 No.6

$Y_2O_3$ 세라믹 소결체를 제작하기 위해, $Y_2O_3$ 분말을 분산한 상태에서 슬러리에 pH 조절제인 NaOH를 첨가하였으며 결합제로는 PVA, 가소제로는 PEG를 첨가하여 열분무 건조 공정을 거쳐 $Y_2O_3$ 과립형 분말을 제조하였다. ${\phi}14mm$ 크기의 $Y_2O_3$ 세라믹 성형체를 성형하고, $1650^{\circ}C$의 온도에서 소결하여 $Y_2O_3$ 세라믹 소결체를 제작하였다. $Y_2O_3$ 소결체의 미세구조, 밀도 및 내플라즈마 특성이 성형압력 및 소결시간에 따라 분석되었다. $Y_2O_3$ 소결체는 $CHF_3/O_2/Ar$ 플라즈마에 노출시켜, $Ar^+$ 이온빔에 의한 물리적반응 식각과 $CHF_3$로부터 분해된, $F^-$ 이온에 의한 화학적반응 식각에 의한 건식 식각 처리가 이루어졌다. 본 연구에서 $Y_2O_3$ 소결체 소결시간의 증가에 따라, 비교적 높은 밀도를 나타내었으며, 내플라즈마 특성이 향상되는 것으로 나타났다. $Y_2O_3$ ceramic specimens were fabricated from the granular powder, obtained by spray drying process from the slurry. The slurry was prepared by mixing PVA binder, NaOH for Ph control, PEG and $Y_2O_3$ powder. The $Y_2O_3$ specimen was shaped in size of ${\phi}14mm$ and then sintered at $1650^{\circ}C$. The characteristics, microstructure, densities and plasma resistance of the $Y_2O_3$ specimens were investigated with the function of forming pressure and sintering time. $Y_2O_3$ specimens were exposed under the $CHF_3/O_2/Ar$ plasma, the dry etching treatment of specimens was carried out by the physical reaction etching of $Ar^+$ ion beam and the chemical reaction etching of $F^-$ ion decomposed from $CHF_3$. With increasing sintering time, $Y_2O_3$ specimens showed relatively high density and strong resistance in plasma etching test.

진동하에서 일방향응고 시킨 Al-CuAl2 공정복합재료의 응고에 관한 연구

이현규,이길홍 ( Hyun Kyu Lee,Kil Hong Lee ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.3

N/A Unidirectional solidification of Al-CuAl₂ eutectic composites was studied under the condition of forced convection by vibration. It has been shown that thermal gradient for solid is different from that for liquid during solidification under force convection by vibration. With increase of vibration, mobility of liquid increases, but decreases with decreasing vibration. The rate of solidification is very high initially, and decreases suddenly. For further solidification, the rate of solidification decrceases slowly, and shows a L-type behavior. The mechanical vibration during solidification effects efficiently on nucleation, and induces a forced convection in liquid. By the forced convection, great thermal gradient of liquid interface between solid and liquid can be obtained. The amount of solute near the interface also decreases as solute distribution is improved by the forced convection. (Received November 14, 1997)

스마트폰 앱 사용의 순효익에 영향을 미치는 요인

이현규(Hyun-Kyu Lee),남영우(Young Woo Nam) 한국인터넷전자상거래학회 2013 인터넷전자상거래연구 Vol.13 No.4

Dramatical changes are occurred in communication and work environment due to the smartphones for the past 5 years. The major usage pattern of smartphone is turned to change from text messages and voice calls to mobile applications that provide useful informations. Social network also becomes very popular word in mobile communications. A mobile application(app) is a software application designed to run on smartphones, tablet computers and other mobile devices. Two thirds of these apps are replaced very frequently, but 7 apps have consistently used for more than one year on the average. So, this research focused on the why these apps are used continually without replacing and what natures of these apps will encourages continual usage. For these research backgrounds, this study extracted technology acceptance and quality factors from D&M model of information system success and Technology Acceptance Theory. We found that net benefit is the most important factor that makes apps to be used continually.

전자상거래 고객가치 요인의 한,중 비교

이현규 ( Hyun Kyu Lee ),한재호 ( Jae Ho Han ) 한국정보시스템학회 2012 情報시스템硏究 Vol.21 No.4

Means-Ends Network model was used to identify factors of means objective(means supplied by vendor) and fundamental objectives(purchasing motivations) for purchasing decision-making structure and dimensions of customer values on purchasers of internet shopping mall in Korea and China. In Means-Ends Network 6 factors(shopping travel, shipping assurance, vendor trust, online payment, product choice, and recommender systems) were found as a means objectives and 3 factors(shopping convenience, internet environment, customer support) as a fundamental objectives of shopping. However the results of hypotheses test for Means-Ends Network show some important differences between two countries. Something important to notice here is that Chinese customers shopping in China recognize shipping assurance factor and vendor trust factor as important factors satisfying all fundamental objectives unlike as in the case of our country. As these two factors are attribution factors responsible to the sellers, it is identified that customers do not trust the sellers and sellers have not met the expectations of customers. Therefore, these results show that the seller efforts assuring the reliability of the seller themselves, such as conducting its own compensation scheme are more important rather than the establishment of the guarantee institution to guarantee reliability and delivery assurance of sellers and implementation of legal and institutional apparatus such as the settlement of e-commerce licence system. Though this study presents such an important marketing implications, it can be pointed out that the limits are this research was done on the general Internet shopping malls without considering the Internet shopping mall types of diversity, the survey was designed around the student samples for convenience of the investigation because it was an international survey and the collected data has been limited to the western coast cities, such as China`s Beijing, Shanghai, and Dalian.

비트 깊이에 따른 볼트 체결응력 해석

이현규(Hyun Kyu Lee),나승우(Seung-Woo Ra),김종봉(Jong-Bong Kim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

As the thickness of IT produce such as mobile phone and watch phone reduce, the size of bolts also should be reduced. These days, bolts of sub-millimeter diameter are used. Even though the bolt size is reduced, the bolt should have enough joining force. The joining force of bolt is dependent on thread shape, screw head thickness, and bit shape. In this study, the effect of bit depth on the joining force is investigated.

초소형 볼트의 Bit 형상에 따른 체결 토크 분석

이현규(Hyun-Kyu Lee),박진아(Jin-Ah Park),김종봉(Jong-Bong Kim) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.4-3