• Journal of Welding and Joining
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• 제30권5호
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• pp.64-69
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• 2012

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.

• 한국재료학회지
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• 제24권9호
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• pp.495-501
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• 2014

Despite having many attractive properties, $ZrO_2$ ceramic has a low fracture toughness which limits its wide application. One of the most obvious tactics to improve its mechanical properties has been to add a reinforcing agent to formulate a nanostructured composite material. Nanopowders of $ZrO_2$ and Cr were synthesized from $CrO_3$ and Zr powder by high energy ball milling for 10 h. Dense nanocrystalline $2/3Cr-ZrO_2$ composite was consolidated by a high-frequency induction heated sintering method within 5 min at $600^{\circ}C$ from mechanically synthesized powder. The method was found to enable not only rapid densification but also the inhibition of grain growth, preserving the nano-scale microstructure. Highly dense $2/3Cr-ZrO_2$ composite with relative density of up to 99.5% was produced under simultaneous application of a 1 GPa pressure and the induced current. The hardness and fracture toughness of the composite were 534 kg/mm2 and $7MPa{\cdot}m1/2$, respectively. The composite was determined to have good biocompatibility.

• 마이크로전자및패키징학회지
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• 제10권1호
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• pp.45-50
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• 2003

시스템 보드에 플립 칩 BGA가 실장된 3차원 유한요소 해석 모델을 구성하여 열사이클시험 과정에서 발생되는 솔더 접합부의 피로수명을 예측하였다. 피로 모델은 Darveaux의 경험식에 기초하여 비선형 점소성 해석을 수행하였다. 해석은 4종류의 열사이클시험 조건과 패드구조, 솔더 볼의 조성과 크기의 변화에 따라 발생하는 크리프 수명을 평가하였다. 해석결과 $-65∼150^{\circ}C$의 열사이클시험 조건에서 가장 짧은 피로수명을 보였으며, $0∼100^{\circ}C$ 조건과 비교하면 약 3.5 배 정도 증가하였다. 동일한 시험조건에서 패드구조 변화에 따른 피로수명 차이는 SMD구조가 NSMD구조에 비해 약 5.7% 증가하였다 결과적으로 솔더 접합부에서 크리프 변형에너지 밀도가 높으면 피로수명은 짧아지는 것을 알 수 있었다

• 한국전기전자재료학회논문지
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• 제23권6호
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• pp.481-486
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• 2010

ENIG (electroless Ni immersion gold) is one of surface finishing which has been most widely used in fine pitch SMT (surface mount technology) and BGA (ball grid array) packaging process. The reliability for package bondability is mainly affected by interfacial reaction between solder and surface finishing. Since the behavior of IMC (intermetallic compound), or the interfacial reaction between Ni and solder, affects to some product reliabilities such as solderability and bondability, understanding behavior of IMC should be important issue. Thus, we studied the properties of ENIG with P contents (9 wt% and 13 wt%), where the P contents is one of main factors in formation of IMC layer. The effect of P content was discussed using the results obtained from FE-SEM(field-emission scanning electron microscope), EPMA(electron probe micro analyzer), EDS(energy dispersive spectroscopy) and Dual-FIB(focused ion beam). Especially, we observed needle type irregular IMC layer with decreasing Ni contents under high P contents (13 wt%). Also, we found how IMC layer affects to bondability with forming continuous Kirkendall voids and thick P-rich layer.

• 한국의류산업학회지
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• 제11권6호
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• pp.867-877
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• 2009

These days, the fantastic in opposition to classic beauty becomes a genre of creative body expression. The purpose of this study was to analyze the expressive characteristics of body types and meanings in recent fantastic fashion illustration. The method of this study was to analyze recent documentaries, fashion books, internet web site and so forth. The results were as follows: In literatures, pictures and movies, the category of the fantastic body's expressive types were classified as dominant mutant based on SF, multi body or fragment body by disruption, heterogeneous compound based on myth, personified humanoid and non substance in supernatural boundary. The dominant mutant based on SF was expressed image morphing, composition of machine image with body and modern metamorphosis of classic SF body. It means propensity to post-feminism and reservation of meaning analysis based on human unconsciousness. The multi body or fragment body by disruption in fashion illustration was expressed distorted composition of same body pictures, replacement of different bodies, deconstruction and partial omission of body and composition of meaning or non meaning images. It means permanence of self and basic narcissism. The heterogeneous compound based on myth was expressed general composition or optical illusion of various and aggressive animal motive. It means reinterpretation of original myth, metaphor of basic femme fatale, pursuit of permanence and sign of primitive mind in unconsciousness. The personified humanoid was expressed real human body description of mannequin or ball joint doll and anthropomorphism of robot image. It means representative satisfaction and nostalgia of childhood. The non substance in supernatural boundary was expressed grotesque description of ghost, zombie, vampire, angel, fairy, using of symbolic red, black color and non body. It means human's basic desire about immortality and taboo. Through the result of these study, the expression of fantastic body in fashion illustration will expend expressive method and we will understand human and cultural codes of today.

• 마이크로전자및패키징학회지
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• 제22권1호
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• pp.35-41
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• 2015

In this study, in order to improve the reliability of ACF interconnections, solder ACF joints were investigated interms of solder joint morphology and solder wetting areas, and evaluated the electrical properties of Flex-on-Board (FOB) interconncections. Solder ACF joints with the ultrasonic bonding method showed excellent solder wetting by broken solder oxide layers on solder surfaces compared with solder joints with remaining solder oxide layer bonded by the conventional thermo-compression (TC) bonding method. When higher target temperature was used, Sn58Bi solder joints showed concave shape due to lower degree of cure of resin at solder MP by higher heating rate. ACFs with epoxy resins and SAC305 solders showed lower degree of resin cure at solder MP due to the slow curing rate resulting in concave shaped solder joints. In terms of solder wetting area, solder ACFs with $25-32{\mu}m$ diameters and 30-40 wt% showed highest wetted solder areas. Solder ACF joints with the concave shape and the highest wetting area showed lower contact resistances and higher reliability in PCT results than conventional ACF joints. These results indicate that solder morphologies and wetting areas of solder ACF joints can be controlled by adjustment of bonding conditions and material properties of solder and polymer resin to improve reliability of ACF joints.

• 마이크로전자및패키징학회지
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• 제15권2호
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• pp.47-54
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• 2008

컴포넌트에서의 비정상적인 금속간화합물 성장이 보드 레벨 기계적 신뢰성에 미치는 영향을 연구하기 위하여, 전기 도금된 Ni/Au UBM과 Sn2.5Ag0.5Cu 솔더의 리플로우 횟수 및 고온 시효 시간에 따른 금속간 화합물 성장거동을 관찰하였다. 각 조건별로 처리된 컴포넌트에서 솔더 접합부의 기계적 특성을 비교하기 위하여, 전단 속도 변화에 따른 볼 전단 시험을 실시하여 전단에너지 값을 측정하였다. 마지막으로, 보드 레벨에서의 기계적 신뢰성 시험을 위하여 조건별로 처리된 컴포넌트를 PCB 보드에 실장하여, 3점 굽힘 시험 및 충격 시험을 실시한 후 파괴모드를 분석하였다.

• 한국콘텐츠학회논문지
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• 제10권11호
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• pp.113-124
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• 2010

북한 애니메이션에 대한 연구는 아직 빈약하며, 특히 기법이나 스타일에 대한 연구는 이뤄지지 않았다. 그래서 본 연구에서는 북한 인형영화의 캐릭터 디자인에 주목하되 북한 인형영화가 양적인 면과 조형의 질적인 면이 눈에 띄게 향상된 1985년경을 중심으로 살펴보았다. 남한과는 달리 북한에서는 애니메이션 제작 초창기부터 인형 영화에 대해 국가적으로 꾸준한 지원이 있었고, 인형영화의 전통이 강한 유럽의 사회주의 국가들과 활발한 교류를 했기 때문에 북한의 인형 영화는 지속적으로 발전할 수 있었으며 1985년부터는 매 해 꾸준히 제작되었다. 1985년에 제작된 캐릭터 디자인에는 구조적인 특징과 표현상의 특징을 확인할 수 있는데, 구조적으로는 철제골격을 사용하여 실험적인 형태와 정확한 관절의 움직임이 가능했고, 표현적으로는 조선화기법을 캐릭터 디자인에 적용하여 북한 인형영화 캐릭터 디자인에 간결함과 명확함, 섬세함이라는 나름의 미학을 정립했다.

• Archives of Reconstructive Microsurgery
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• 제20권1호
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• pp.38-42
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• 2011

Purpose: To evaluate the effect of intermittent bleeding method in the distal phalanx replantation. Materials and Methods: From January 2007 through June 2009, authors have replanted 117 cases of distal phalangeal amputation in adults at Soo Hospital and Chonbuk National University Hospital. Cases of zone II were 60 cases and zone III 57 according to Allen classification. Male to female ratio was 8.7:1.3. The most common cause was machinery injury in the factory, 98 cases(83.8%), next one was belt injury of the machine, 11 cases(9.4%) and others, 8(6.8%). At least one digital artery and digital nerve were anastomosed under the operating microscope, but vein was impossible to anastomosis as unable to find out in the zone II and III. After anastomosis of one or more digital arteries and nerves, heparine(6,000-10,000 units) was kept to intravenous injection for 24 hours and at the same time fish mouth incision in 2-3 millimeter diameter was made in the distal radial and ulnar margin of the replanted distal phanlanx. From the first 30 minutes to an hour after replantation, incision site was swabbed with heparinized cotton ball for 5 minutes in every 30 to 40 minutes to make sure perfusion for 24 hours, every an hour at the second day, every two hours at the postoperative third to fifth day. Results: 92 cases(78.6%) was completely survived at average postoperative third week follow-up and satisfied with preservation of the finger nail, digit length, good range of motion of the distal interphalangeal joint and acceptable sensibility at average 1.2 years follow-up. Conclusions: Intermittant bleeding method in replantation of crushed distal phalanx impossible to anastomosis of vein at zone II and III of Allen classification was regarded as one of the notable salvage procedure.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.82-82
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• 2010

표면실장 공법을 통해 CSP 패키지를 보드에 실장 하는데 있어 무연솔더 접합부의 신뢰성에 영향을 미치는 인자 중 가장 중요한 것은 접합부에 형성되는 IMC (Intermetallic compound, 금속간화합물)인 것으로 알려져 있다. 접합부의 칩 부분에는 솔더와 칩의 UBM (Under bump metalization)이 접합하여 IMC가 형성되나, 보드 부분에는 솔더와 보드의 UBM 뿐만 아니라 그 사이에 솔더 페이스트가 함께 접합되어 IMC가 형성된다. 본 연구에서는 패키지의 신뢰성 연구를 위해 솔더 페이스트의 유무 및 두께에 따른 무연 솔더 접합부의 미세조직의 변화를 분석하였다. 본 실험에서는 Sn-3.0(Wt.%)Ag-0.5Cu 조성과 본 연구진에 의해 개발된 Sn-Ag-Cu-In 조성의 직경 $450{\mu}m$ 솔더 볼을 사용하였으며, 솔더 페이스트는 상용 Sn-3.0Ag-0.5Cu (ALPHA OM-325)를 사용하였다. 칩은 ENIG (Electroless nickel immersion gold) finish pad가 형성된 CSP (Chip scale package)를, 보드는 OSP (Organic solderability preservative)/Cu finish pad가 형성된 것을 사용하였다. 실험 방법은 보드를 솔더 페이스트 없이 플라즈마 처리 한 것, 솔더 페이스트를 $30{\mu}m$ 두께로 인쇄한 것, $120{\mu}m$의 두께로 인쇄한 것, 이렇게 3가지 조건으로 준비한 후, 솔더 볼이 bumping된 칩을 mounting하여, $242^{\circ}C$의 peak 온도 조건의 oven(1809UL, Heller)에서 reflow를 실시하여 패키지를 형성하였다. 이후 시편은 정밀 연마한 후, OM(Optical Microscopic)과 SEM(scanning electron microscope) 및 EDS(energy dispersive spectroscope)를 사용하여 솔더 접합부 IMC의 미세조직을 관찰, 분석하였다.