• 한국의학물리학회지:의학물리
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• 제9권3호
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• pp.137-141
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• 1998

납공 (lead ball)과 쇠공(steel ball)을 고에너지 광자선에 대한 차폐재로 이용하는 것이 가능한가를 평가하고 ,4～10MV 엑스선 차폐를 위한 납공과 쇠공의 물리자료를 구하는 것이 목적이다. 직경이 각각 2.0-2.5mm, 1.5-2.0mm 인 납공 및 쇠공을 폭이 균일한 아크릴 용기에 채워, 두께의 균일성 확인을 위해 MV 엑스선사진을 촬영하였으며, 금속공의 평균 밀도와 4～10MV 엑스선에 대한 선감쇠계수를 측정하였다. 선감쇠계수를 측정할 때 Farmer 이온함을 이용하였으며 산란선의 효과를 최소화하기 위해 70cm 거리에서 조사면크기는 5.5cm$\times$5.5cm로 하였다. 비교하기 위해 납판과 철판에 대해서도 같은 종류의 변수를 구하였다. 금속구를 용기에 채웠을 때 분포는 균일하였으며, 납 -공기 혼합물의 밀도는 6.93g/$cm^3$이었으며, 철-공기 혼합물의 밀도는 4.75g/$cm^3$ 이었다. 납의 밀도에 대한 납-공기 혼합물의 밀도의 비는 0.611, 철에 대한 철-공기 혼합물의 밀도의 비는 0.604이었다. 납-공기 혼합물의 반가층은 4MV, 6MV, 10MV 엑스선 각각에 대하여 1.89cm, 2.07cm, 2.16cm 이었으며 납판 반가층의 약 1.64배였다. 철-공기 혼합물의 반가층은 4MV, 6MV, 10MV 엑스선 각각에 대하여 3.24cm, 3.70cm, 4.15cm 이었으며 철판 반가 층의 약 1.65 배였다. 금속구는 용기속에 고르게 채워질 수 있기 때문에 차폐재료로 쓸 수 있다. 납공과 쇠공이 고르게 채워질 때 밀도는 각각 6.93g/$cm^3$, 4.75g/$cm^3$ 이었으며 각각의 반가층은 납 또는 철의 반가층의 1.65배였다. 밀도와 반가층을 곱한 값은 공이나 판에 대해 같은 값이었다.

• 한국콘텐츠학회논문지
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• 제11권3호
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• pp.262-270
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• 2011

본 연구는 swiss ball LSE에 따른 하지 경직도, 균형 및 보행에 관한 효과를 알아보고자 BBS, FRT, 수정된 Ashworth 척도(MAS), TUG 측정 분석 하였다. 대상자는 H병원에서 입원 또는 통원치료를 받고 있는 뇌졸중 환자 중 선정기준에 적합한 34명을 고전적 신경물리치료군 17명, swiss ball LSE 실시군에 17명씩 할당하여 하지의 균형능력은 BBS와 FRT, 경직도는 MAS, 보행능력은 TUG를 사용하여 비교 분석하였다. Swiss ball LSE군에서 BBS와 FRT는 유의하게 증가하였으며, MAS와 TUG는 유의하게 감소하였다. 또한 군간의 비교에서는 FRT와 MAS에서 유의한 차이가 나타났다. 결과적으로 swiss ball LSE는 뇌졸중 환자의 하지 근경직, 균형능력 및 보행능력을 회복시킬 수 있는 것으로 사료된다.

• 한국공작기계학회논문집
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• 제10권4호
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• pp.97-103
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• 2001

The study on the high-speed machine tool is very important for the improvement of productivity since it can shortens cutting and non-cutting time. Especially, high speed of feed drive system is the major research field. In the industries of the advanced countries, the feed drive systems at the speed of 60 m/min have been already developed based on the high lead ball screws. In this study, a high speed feed drive system at the speed of 60 m/ min has been developed, and its movements characteris-tics are investigated. As the movement characteristics, positioning accuracy, angular accuracy, straightness and micro step-response are measured. Thermal characteristics of the system is also discussed. For measuring the movement characteris-tics, a laser interferometer, a memory-based Hi-coder and a cooling device are used. The experimental results confirm that the movement characteristics and the thermal behavior of the system are satisfactory in the aspect of accuracy and stability.

• 한국안전학회지
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• 제25권6호
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• pp.14-21
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• 2010

A miniature single solder ball joint is designed to mimic the actual solder joints used in the micro-electric industries. Shear tests were conducted to evaluate the mechanical behavior of miniature single solder joints at intermediate strain rates from $0.019\;s^{-1}$ to $2.16\;s^{-1}$ at room temperature. The shear fracture strength of the present solder ball joints generally increased with increasing shear strain rate, ranging from 32 to 51MPa. This behavior is affected by the sensitivity of bulk solder strength to strain rate. Shear fracture mode changed from brittle to partial ductile (failure inside the bulk solder) with an increase of shear speed. The unloading shear fracture toughness is generally consistent with the measure of the amount of bulk solder on the fractured surface.

• 반도체디스플레이기술학회지
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• 제6권1호
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• pp.17-22
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• 2007

Recent new packages such as MCP(Multi-Chip Package), QDP(Quadratic Die Package) and DDP(Dual Die Package) have stack type configuration. This kind of multi-layer package is thicker than single layer package. So there is need for the low height looping technology in wirebonder to make these packages thinner. There is stiff zone above ball in wirebonder wire which is called HAZ(Heat Affect Zone). When making low height loop (below $80\;{\mu}m$) with traditional forward loop, stiff wire in HAZ(Heat Affected Zone) above ball is bended and weakened. So the traditional forward looping method cannot be applied to low height loop. SSB(stand-off stitch) wire bonding method was applied to many packages which require very low loops. The drawback of SSB method is making frequent errors at making ball, neck damage above ball on lead and the weakness of ball bonding on lead. The alternative looping method is BNL(ball neckless) looping technology which is already applied to some package(DDP, QDP). The advantage of this method is faster in bonding process and making little errors in wire bonding compared with SSB method. This paper presents the result of BNL looping technology applied in assembly house and several issues related to low loop height consistence and BNL zone weakness.

• 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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.573-574
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• 2009

• 한국세라믹학회지
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• 제30권8호
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• pp.623-628
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• 1993

Lead monoxide has two phases at room temperature. One is a yellow orthorhombic phase, the other is a redtetragonal phase. Sometimes two phases are hybrided. The specificity of phase transitions of lead oxide is found during the milling of the batch including lead oxide. The pure orthorhombic phase of PbO can be transformed to the tetragonal phase perfectly by wet ball milling (milling liquid is distilled water) without thermal energy. However, when ethyl alcohol, isopropyl alcohol and aceton are used as milling liquid, respectively, the hybrid form of orthorhombic andtetragonal phases is obtained by wet ball milling. From the hybrid form heat-treated at $600^{\circ}C$ for 3hrs, this work results that mechanical phase transition of orthorhombic phase make a new form as distorted type orthorhombic phase of PbO.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.865-868
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• 2002

This study investigated the shape deformation of ball projectile(5.56mn) under the low energy impact by the use of the drop weight impact tester. ball projectile(5.56mm) consisted of the copper face with a lead core. The impact conditions were changed with the variations of the mass and the drop height of the impact tup. Shape deformation of ball projectile(5.56mm) after low velocity impact was measured using a video microscope and CCD camera. The test result showed that impact energy by changing of drop height of the impact tup affected shape deformation of ball projectile(5.56mm). So, it is important to study the relativity between shape deformation of ball projectile(5.56mm) and ballistic protection of plate(such as hybrid composite laminates) under the high velocity impact.