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안지혁,김광석,이영철,김용일,정승부,Ahn, Jee-Hyuk,Kim, Kwang-Seok,Lee, Young-Chul,Kim, Yong-Il,Jung, Seung-Boo 한국마이크로전자및패키징학회 2010 마이크로전자 및 패키징학회지 Vol.17 No.3
We reported the methodology for the shear test which is one of the evaluation procedure for mechanical reliability of flip-chip package. The shear speed and the tip height are found to be two significant experimental parameters in the shear test. We investigated how these two parameters have an influence on the results, the shear strength and failure mode. In order to prove these experimental inconsistency, simulation using finite element analysis was also conducted to calculate the shear strength and to figure out the distribution of plastic energy inside of the solder ball. The shear strength decreased while the tip height increased or the shear speed decreased. A variation in shear strength due to inconsistent shear conditions made confusion on analyzing experimental results. As a result, it was strongly needed to standardize the shear test method. 본고에서는 마이크로 접합을 위한 솔더볼 또는 범프의 기계적 신뢰성 평가에 사용되는 전단시험의 표준화 규격에 대해 고찰해 보았다. 전단시험에서 중요한 실험 조건 중 하나인 전단속도는 low speed shear test와 high speed shear test로 구분 된다. 전단속도가 빨라질수록 솔더볼에 가해지는 충격이 커지기 때문에, 소성변형에 대한 저항성이 커지게 되고, 전단강도가 커지게 된다. 그리고 이 결과는 전산모사를 통하여 확인할 수 있다. 또 하나의 중요한 실험 조건으로 전단툴의 높이가 있다. 일반적으로 전단툴의 높이가 높을수록 전단강도 값은 낮아지게 되는데, 여러 국제 규격에서 제시한 솔더볼 높이의 25% 지점을 초과한 높이에서 전단시험을 진행했을 때에는 전단시험이 진행되는 접합 계면의 면적이 줄어들어 실험결과의 신뢰도가 떨어지게 된다. 이와 같이 전단속도와 툴의 높이 등의 실험조건들이 구체적으로 규격화 되어있지 않은 채 진행 되면, 실험 결과의 신뢰도가 떨어지고, 각 계에서 진행된 연구결과를 상호 비교하기가 어렵다. 따라서 효율성을 고려한 간접 시험법 개발 및 최신 패키징기술을 반영된 특성평가 시험법의 규격, 그리고 다양한 시험 표준화는 결국 마이크로 전자패키지의 고 신뢰성으로 나타날 것이라 생각된다.
니알브론즈의 기계적 특성에 미치는 알루미늄 및 지르코늄 함량의 영향
안지혁 ( Jee Hyuk Ahn ),김동욱 ( Dong Wook Kim ),김민수 ( Min Soo Kim ),황종현 ( Jong-hyun Hwang ),한승전 ( Seung Zeon Han ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.8
To study the effect of Al and Zr contents on the microstructural changes and tensile properties of Ni-Al-Bronze alloy, seven specimens were cast with different Al and Zr contents. The microstructure observation revealed that all specimens were composed of β` and κ phases in a α matrix. With increasing Al and Zr contents, the tensile strength of the Ni-Al-Bronze increased, due to an increase in the β` and κ phase fraction and grain refinement, but the elongation behavior of the Ni-Al-Bronze declined. Furthermore, the excessive addition of Zr caused a reduction in tensile strength and ductility. A successful combination of tensile strength and ductility, 688 MPa-23% was achieved by the controlled addition of Zr to Ni-Al-Bronze. (Received November 10, 2016; Accepted March 13, 2017)
Sn-58Bi 솔더 페이스트와 ENIG 표면 처리된 기판 접합부의 계면 반응 및 접합강도
신현필,안병욱,안지혁,이종근,김광석,김덕현,정승부,Shin, Hyun-Pil,Ahn, Byung-Wook,Ahn, Jee-Hyuk,Lee, Jong-Gun,Kim, Kwang-Seok,Kim, Duk-Hyun,Jung, Seung-Boo 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.5
Sn-Bi eutectic alloy has been widely used as one of the key solder materials for step soldering at low temperature. The Sn-58Bi solder paste containing chloride flux was adopted to compare with that using the chloride-free flux. The paste was applied on the electroless nickel-immersion gold (ENIG) surface finish by stencil printing, and the reflow process was then performed at $170^{\circ}C$ for 10 min. After reflow, the solder joints were aged at $125^{\circ}C$ for 100, 200, 300, 500 and 1000 h in an oven. The interfacial microstructures were obtained by using scanning electron microscopy (SEM), and the composition of intermetallic compounds (IMCs) was analyzed using energy dispersive spectrometer (EDS). Two different IMC layers, consisting of $Ni_3Sn_4$ and relatively very thin Sn-Bi-Ni-Au were formed at the solder/surface finish interface, and their thickness increased with increasing aging time. The wettability of solder joints was investigated by wetting balance test. The mechanical property of each aging solder joint was evaluated by the ball shear test in accordance with JEDEC standard (JESD22-B117A). The results show that the highest shear force was measured when the aging time was 100 h, and the fracture mode changed from ductile fracture to brittle fracture with increasing aging time. On the other hand, the chloride flux in the solder paste did not affect the shear force and fracture mode of the solder joints.
티타늄이 첨가된 알루미나 분산강화 동합금의 산화물 형성 거동
조홍래,한승전,안지혁,이재현,손영국,김광호,Joh, Hongrae,Han, Seung Zeon,Ahn, Jee Hyuk,Lee, Jehyun,Son, Young Guk,Kim, Kwang Ho 한국재료학회 2015 한국재료학회지 Vol.25 No.4
Alumina dispersion strengthening copper(ADSC) alloy has great potential for use in many industrial applications such as contact supports, frictional break parts, electrode materials for lead wires, and spot welding with relatively high strength and good conductivity. In this study, we investigated the oxidation behavior of ADSC alloys. These alloys were fabricated in forms of plate and round type samples by surface oxidation reaction using Cu-0.8Al, Cu-0.4Al-0.4Ti, and Cu-0.6Al-0.4Ti(wt%) alloys. The alloys were oxidized at $980^{\circ}C$ for 1 h, 2 h, and 4 h in ambient atmosphere. The microstructure was observed with an optical microscope(OM) and a scanning electron microscope(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS). Characterization of alumina was carried out using a 200 kV field-emission transmission electron microscope(TEM). As a result, various oxides including Ti were formed in the oxidation layer, in addition to ${\gamma}$-alumina. The thickness of the oxidation layer increased with Ti addition to the Cu-Al alloy and with the oxidation time. The corrected diffusion equation for the plate and round type samples showed different oxidation layer thickness under the same conditions. Diffusion length of the round type specimen had a value higher than that of its plate counterpart because the oxygen concentration per unit area of the round type specimen was higher than that of the plate type specimen at the same diffusion depth.
LED 패키지 솔더 접합부의 기계적 신뢰성에 미치는 열처리의 영향
고민관 ( Min Kwan Ko ),안지혁 ( Jee Hyuk Ahn ),이영철 ( Young Chul Lee ),김광석 ( Kwang Seok Kim ),윤정원 ( Jeong Won Yoon ),정승부 ( Seung Boo Jung ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.1
We studied the effect of heat treatment on the microstructures and mechanical strength of the solder joints in the Light Emitting Diode (LED) packages. The commercial LED packages were mounted on the a flame resistance-4 (FR4) Printed Circuit Board (PCB) in the reflow process, and then the joints were aged at 125℃ for 100, 200, 300, 500 and 1000 hours, respectively. After the heat treatment, we measured the shear strength of the solder joints between the PCB and the LED packages to evaluate their mechanical property. We used Pb-free Sn-3.0Ag-0.5Cu solder to bond between the LED packages and the PCBs using two different surface finishes, Electroless Nickel-Immersion Gold (ENIG) and Electroless Nickel-Electroless Palladium-Immersion Gold (ENEPIG). The microstructure of the solder joints was observed by a scanning electron microscope (SEM). (Cu,Ni)6Sn5 intermetallic compounds (IMCs) formed between the solder and the PCB, and the thickness of the IMCs was increased with increasing aging time. The shear strength for the ENIG finished LED package increased until aging for 300 h and then decreased with increasing aging time. On the other hand, in the case of an ENEPIG finished LED package, the shear strength decreased after aging for 500 h.
SM45C 강의 narrow gap 용접부 회전굽힘 피로 특성
한승전 ( Seung Zeon Han ),안지혁 ( Jee Hyuk Ahn ),이재현 ( Je Hyun Lee ),김상식 ( Sang Shik Kim ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.11
SM45C steel was welded by conventional CO2 arc and narrow gap welding (NGW). The fatigue strength of NGWed sample had a value about 90 MPa higher than that of the CO2 arc welded sample. The width of welding and heat affected zone in NGWed samples decreased about 40% compared to the conventional CO2 arc welded sample. The hardness value of the welding zone in the NGW sample was 33.3% higher than that of the CO2 arc welded sample. The microstructure change of the SM45C during NGW revealed that the matrix was transformed to the martensite phase. With the small width of welding and heat affected zone in the NGW, therefore, the specimen with NGW had a faster cooling rate after welding. We therefore concluded that the hardness was increased by hard martensite formation during cooling after NGW, and this increase in hardness resulted in better fatigue strength of SM45C steel compared to conventional CO2 arc welding. (Received March 13, 2014)
Cu가 첨가된 Zn-Al 합금에서 일방향응고 및 냉간인발에 따른 기계적 특성 향상
정해창 ( Hae Chang Jeong ),김민수 ( Min Soo Kim ),안지혁 ( Jee Hyuk Ahn ),임성환 ( Sung Hwan Lim ),한승전 ( Seung Zeon Han ),이재현 ( Jehyun Lee ),김광호 ( Kwang Ho Kim ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.8
The lamellar structure of two phases, the Zn-rich and Al-rich phases, is formed in a Zn-5 wt% Al eutectic alloy. In order to study the effect of microstructural changes on the tensile properties of eutectic Zn-Al binary alloy, Zn-Al and Zn-Al-Cu alloys were directionally solidified at a growth rate of 50 μm/s using a Bridgman-type method. The alloys were successively drawn until reaching area reductions of 50% and 80% at room temperature. The tensile strength of the Zn-Al alloy decreased with increasing drawing ratio. In the Zn-Al-Cu alloy, the tensile strength increased until the area reduction reached 50%, but decreased at an area reduction of 80%. The ductility of alloys prepared by directional solidification increased with increasing drawing ratio. The orientations of the lamellar structure and grains were aligned in the drawn direction. The inter-lamellar distance of the alloys also decreased with increasing drawing ratio. As a result, the trade-off between strength and ductility could be significantly reduced. The strength and ductility combination of 246 MPa-40% was achieved by cold drawing with 80% area reduction of the Zn-Al-Cu alloy. (Received January 10, 2017; Accepted March 27, 2017)
김광석 ( Kang Seok Kim ),이영철 ( Young Chul Lee ),안지혁 ( Jee Hyuk Ahn ),송준엽 ( Jun Yeob Song ),유중돈 ( Chong D. Yoo ),정승부 ( Seung Boo Jung ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.11
In the development of 3D package, through silicon via (TSV) formation technology by using deep reactive ion etching (DRIE) is one of the key processes. We performed the Bosch process, which consists of sequentially alternating the etch and passivation steps using SF6 with O2 and C4F8 plasma, respectively. We investigated the effect of changing variables on vias: the gas flow time, the ratio of O2 gas, source and bias power, and process time. Each parameter plays a critical role in obtaining a specified via profile. Analysis of via profiles shows that the gas flow time is the most critical process parameter. A high source power accelerated more etchant species fluorine ions toward the silicon wafer and improved their directionality. With O2 gas addition, there is an optimized condition to form the desired vertical interconnection. Overall, the etching rate decreased when the process time was longer.