• 한국지반신소재학회논문집
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• 제17권4호
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• pp.169-177
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• 2018

유리섬유강화폴리에스테르 복합소재는 지중 매설 파이프, 탱크용 구조재, 선체 등 가혹한 환경에서 구조재로 널리 사용되고 있으며, 장기 내수성을 필요로 하는 소재이다. 특히, 물에 잠겨 있을 때 삼투압으로 인하여 겔코트와 복합소재의 박리 등 열화가 진행된다. 본 연구에서는 지중 매설 파이프로 활용되는 GFRP 복합소재의 내구성 향상을 위해 인퓨전(진공성형) 공정으로 UPE (unsaturated polyester) 겔코트 표면 처리한 복합소재를 제작하여, 고온 수침 환경 ($65^{\circ}C$, $75^{\circ}C$, $85^{\circ}C$)에서의 표면 결함 및 크랙 발생과 경도 변화 특성을 확인하였다. 마이크로 CT 단층 촬영을 통하여 수침 온도에 따른 크랙의 침투 깊이를 조사하였으며, $75^{\circ}C$와 $85^{\circ}C$ 조건에서 크랙이 복합소재까지 침투하여 내구성을 저하시키는 것으로 확인되었다. 최초 크랙이 발생하는 지점을 고장시간으로 정의하고 아레니우스식을 활용하여 $23^{\circ}C$ 상온에서의 수명 예측을 실시하였다. 본 연구로 토목, 건축, 해양산업분야 등 겔코트가 적용되는 다양한 산업분야의 신뢰성 평가에 응용될 수 있을 것으로 기대된다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2004년도 ISMP Pb-free solders and the PCB technologies related to Pb-free solders
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• pp.233-241
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces strictly related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2004년도 ISMP Pb-free solders and the PCB technologies related to Pb-free solders
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• pp.211-219
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces stric시y related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials. In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• 한국산학기술학회논문지
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• 제15권6호
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• pp.3396-3402
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• 2014

세라믹 사출공정(CIM)으로 성형되는 전자제품 케이스와 같은 판상 제품은 강도 보장을 위한 형상설계가 매우 중요하다. 본 연구에서는 CIM으로 성형된 판상 시편의 두께에 따른 3점 굽힘 시험을 통해 굽힘 강도 및 탄성계수를 도출하여 기계적 특성을 분석했다. 두께 0.48mm 시편은 파단하중이 82.9~94.5N이고, 1.0mm 시편은 233.6~345.8N으로 측정되었다. 시편의 두께가 0.5mm 증가했을 때, 파단하중은 3배가 증가하고 탄성계수는 20%가 감소하는 경향을 확인할 수 있었다. 또한 비커스 경도시험을 통해 시편의 두께가 두꺼워질수록 상대밀도와 표면경도가 작아지는 것을 보였다. 이러한 현상은 두께가 두꺼울수록 소결공정 이후 세라믹 혼합물 중 세라믹 분말의 체적분율이 작아지기 때문으로, 이에 따라 기계적 물성이 부분적으로 변할 수 있음을 실험과 해석결과 비교 분석을 통해 밝혔다.

• 보존과학연구
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• 통권29호
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• pp.65-90
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• 2008

This study examines the status and the physical features of Paraloid B-72 layers with examination of microstructure and analysis of organic matters. Paraloid B-72 layers were coated on samples from the colour layer of outer wall painting in Mireuk hall in Geumsan temple. On the basis of the previous examination result, it has made the samples which are similar to outer wall in Mireuk hall in Geumsan temple. The samples can be divided into two, one; 5% Paraloid B-72 coating and another is without coating. Then samples have been experimented under the compulsive environments of infrared radiation and immersion, thereafter compared the results of the damages and physical features between two samples. As a result of the comparison, the sample with Paraloid B-72 had more serious cracks, exfoliations and peeling layers than that of without Paraloid B-72. Otherwise, in the examination of ultraviolet radiation, the sample with Paraloid B-72 coating showed weaker physical properties, less density in structure of colour layer and less hardness in surface of colour layer than the sample without coating. The percentage of moisture content after the ultraviolet radiation was higher in the sample without Paraloid B-72 than the sample with Paraloid B-72 coating. Observing the conditions before the ultraviolet radiation, the sample with Paraloid B-72 coating demonstrated lower rate in moisture evaporation rate than the sample without Paraloid B-72. As a consequence, in examination of this samples, the change of physical features are increased in the sample with Paraloid B-72 coating than that without Paraloid B-72 when compulsive environment of heat, moisture and ultraviolet rays for a short term are imposed.

• 한국전산유체공학회지
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• 제18권3호
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• pp.67-71
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• 2013

Recently, the rapid development of the semiconductor industry induces the prompt technical progress in the area of device integration and the application of large diameter wafers for the price competitiveness. As a result of the usage of large wafers in the semiconductor industry, the silicon carbide components which have layers of silicon carbide on graphite or RBSC substrates is getting widely used due to the advantages of SiC such as high hardness and strength, chemical and ionic resistant to all the environments superior than other ceramic materials. For the uniform and homogeneous deposition of silicon carbide on these huge components, it needs to know about the gas flow in the CVD reactor, not only for the delicate adjustment of the process variables but more essentially for the cost reduction for the shape change of specimens and their holders on the stage of reactor. In this research, the CFD simulation is challenged for the prediction of the inner distribution of the gas velocity. Chemical reaction simulation is used to predict the distribution of concentration of the reacting gas with the rotating velocity of the stage. With the increase of the rotating speed, more uniform distribution of the reacting gas on the surface of the stage was obtained.

• 한국측량학회지
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• 제21권2호
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• pp.155-164
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• 2003

측량분야에 있어서 무프리즘 토털스테이션의 등장은 많은 분야에서 응용가능성을 가져왔고 지형측량을 비롯한 시설물 측량에서도 그 예외는 아니다. 본 연구에서는 무프리즘 토털스테이션을 이용하여 측량을 수행할 경우 발생할 수 있는 문제점이나 오차 등에 관해 실험을 수행하고 그 적용성과 정확도를 평가하고자 한다. 이를 위하여, 대상물의 재질과 관측각도에 따른 정확도의 변화를 점검하고 거리에 비례한 레이저의 확산과 대상물의 색상이 정확도에 미치는 영향을 분석하였다. 또한, 시설물을 대상으로 실측을 수행하고 그 결과를 분석함으로서 무프르즘 토털스테이션의 시설물 측량 활용성 여부를 판단하였다. 연구결과, 무프리즘 토털스테이션의 관측정확도는 대상물의 경도나 재질과는 관계없으며, 시설물 측량을 위해서는 합초동축시스템을 갖춘 무프리즘 토털스테이션을 이용해야 양호한 결과가 도출됨을 알 수 있었다.

• 청정기술
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• 제17권4호
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• pp.353-362
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• 2011

빗물 활용은 건전한 물 순환 개념에서 중요하며, 신도시 개발 등으로 증가되는 불투수면의 증대에 따른 영향을 해소시키는 방법 중의 하나가 되므로 빗물 처리 시스템의 개선을 통한 수질 개선 방안을 연구하였다. 대전서남부지구의 개발 전 빗물 유출계수는 0.40이었으나 개발 후의 유출계수는 0.59로 산정되었다. 필터를 통과한 우수의 Cu, As, Cr, Fe, Mn 등 중금속 함량은 지하수의 중금속 함량보다 양호하였으며, 집수된 빗물의 수질은 경도, 과망간산칼륨소비량, 염소이온, 증발잔류물, 황산이온, 질산성질소 등의 항목에서는 지하수의 수질보다 양호한 것을 보여 주었으며, 중수도 수질기준을 충족시키는 것으로 확인되었다. 100일 이상 장기 저장 시에도 화장실 용수, 조경 용수 등으로 적합하였다. 종전의 빗물집수 시스템에 덮개가 있는 gutter 설치, 적합한 필터 사용 및 저장조의 지하설치 등으로 시스템을 개선하면 집수되는 수질을 100일 정도 양호하게 유지할 수 있는 것을 확인하였다.

• 한국재료학회지
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• 제11권5호
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• pp.413-418
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• 2001

황산구리 전해욕에 분산제인 콜리이달 실리카($SiO_2$현탁액)를 첨가시키는 분산도금의 방법을 이용하여 음극에 석출하는 전해 석출물의 결정구조, 표면형상, 결정방향 등의 변화를 검토하였고 내식성, 물리적 특성 또한 조사하였다. 콜로이달 실리카를 분산시킨 구리 전해욕의 석출피막의 특성에 대해서 조사한 결과, 다음과 같은 결론을 얻었다. 전해 석출피막의 결정입자가 미세화 되고, 균일하게 성장됨은 물론, 결정 수가 증가하였으며, 콜로이달 실리카의 분산 효과에 의해서 전해 석출피막의 경도가 대략 16%까지 상승하였다. 또한 콜로이달 실리카를 분산시킨 극리 전착층의 X-선 회절패턴이 (111)면, (200)면과 (311)면이 거의 소멸되어 우선 방위가 (111)에서 (110)면으로 변화되었다. 부식전위의 측면에서도 콜로이달 실리카의 흡착 효과에 의해서 구리 전착층의 전위가 귀하게 이동하는 효과를 얻을 수 있었다.

• Journal of Welding and Joining
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• 제27권4호
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• pp.73-78
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• 2009

Characterization of the microweld CCFL electrode for the TFT-LCD backlight unit was carried out in terms of the glass beading heat treatment conditions. We evaluate the weld zone and parent metal of the microweld CCFL electrodes that were exposed to simulated glass beading heat treatment. The CCFL electrode was composed of the cup made with pure Ni, the pin made with pure Mo and the lead wire made with Ni-Mn alloy. Each part of the electrode was assembled together by micro spot welding process and then the assembled electrodes were exposed to simulated glass beading temperatures of $700^{\circ}C,\;750^{\circ}C$ and $800^{\circ}C$. The microstructures of the microweld CCFL electrode were observed by using optical microscope, scanning electron microscope and EDS. Micro-tensile and microhardness test were also carried out. The results indicated that the grain coarsening in the HAZs(heat affected zones) for both the cup-pin weld and pin-lead wire were exhibited and the grain coarsening of the HAZ for the cup and the lead wire was more obvious than the HAZ of the pin. The micro-tensile test revealed that the fracture occurred at the cup-pin weld zone for all test conditions. The fracture surface could be classified into two parts such as pin portion and cup portion including weld nugget. The failure was seemed to be initiated from the boundary between nugget and pin through the weld joint. The result of the microhardness measurement exhibited that the relatively low hardness value, about 105HV was recorded at the HAZ of the cup. This value was about 50% less than that of the original value of the cup. The reduction of the microhardness was considered as the cause of the grain coarsening due to welding process. It was also appeared that there was no change in electric resistance for the standard electrodes and heat treated electrodes.