• 마이크로전자및패키징학회지
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• 제17권2호
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• pp.41-47
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• 2010

PCB와 BGA 패드의 형태가 무연솔더 접합부의 기계적 특성에 미치는 영향을 연구하었다. 현재 BGA/PCB 패드의 형태는 NSMD (Non-Solder Mask Defined)와 SMD (Solder Mask Defined) 두 가지 구조로 형성되어 있다. 본 연구에서는 OSP 도금처리한 무연솔더(Sn-3.0Ag-0.5Cu, Sn-1.2Ag-0.5Cu)의 패드 형태를 NSMD, SMD로 달리하여 낙하충격시험, 굽힘충격시험, 고속전단시험을 통한 솔더 접합부의 기계적 특성을 연구하였다. 낙하충격과 굽힘충격시험의 경우 패드 구조에 따른 솔더볼 접합부의 특성수명은 동일한 경향을 나타내었으며, 솔더접합부의 기계적 특성은 SMD가 NSMD보다 우수하였다. 이 이유는 SMD의 경우 낙하충격 시험과 고속 전단시험 모두 IMC에서 파단이 일어난 반면에 NSMD의 경우 낙하충격 시험 후의 파단면은 패턴을 감싸고 있는 랜드 상단 모서리 부분에서 파단이 일어났기 때문인 것으로 판단된다. 전단시험의 경우에는 NSMD 접합부에서 패드 lift현상이 발생하였다. 따라서 BGA/PCB의 패드구조의 조합은 SMD/SMD > SMD/NSMD > NSMD/SMD > NSMD/NSMD 순으로 기계적 특성 수명이 우수하였다.

• 한국잠사곤충학회지
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• 제40권1호
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• pp.70-77
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• 1998

This study was carried out in order to find out the relationship between physical and chemical properties of silk fiber treated by concentrated calcium nitrate solution. The tensile, thermal and dynamic mechanical properties are also examined on Ca(NO3)2 treated silk fibers. The tensile properties of silk fibers treated by calcium nitrate changed with a concentration. The thermal behavior were also affected by the concentration of calcium nitrate. The degradation temperature (endotherms) and glass transition temperature shifted to lower temperature as the treated concentration increased. It is thought that the physical properties are strongly related to the structure and morphology of Ca(NO3)2 treated silk fibers. As a result, these give property changes with a concentration dependence.

• 대한기계학회논문집
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• 제18권11호
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• pp.2894-2901
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• 1994

Many researchers presented a probabilistic and statistical property of the material strength. However, the study on probabilistic and statistical property of fatigue fracture toughness has not been nearly presented. Major objectives in this paper are to compare the statistical test results of fatigue fracture toughness with those obtained in the tensile experiments, and to recognize the size effect for the probabilistic and statistical property by using specimens with various thickness.

• Journal of Welding and Joining
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• 제21권2호
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• pp.64-69
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• 2003

The bonding phenomena and mechanical property of duplex stainless steel during brazing have been investigated. The UNS32550 was used for base metal, and the MBF50 was used for insert metal. Brazing was carried out under the various conditions (brazing temperature : 1473K, 1498K, holding time : 0∼1.8ks). There were various microconstituents in the bonded interlayer because of reaction between liquid insert metal and base metal. In the early stage of brazing, BN is formed in the bonded interlayer and base metal near the bonded layer. Cr made is formed in the bonded interlayer. The amount of BN and Cr nitrides decrease with the increase of bonding temperature and holding time. Superior shear strength of 550MPa is obtained by restraining the formation of nitrides. (Received January 17, 2003)

• 대한기계학회논문집A
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• 제27권10호
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• pp.1661-1666
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• 2003

The purpose of this study is to develop the simplified model of the crankshaft in the large marine engine for dynamic analysis. Because the actual engine system is under complex dynamic loading condition and it has multi-cylinder, the dynamic analysis is purchased at a high computation cost. In spite of this burden, the dynamic analysis must be perfonned to assure structural integrity of operating marine engine. Therefore, simplification of the analytic model is necessary for dynamic analysis. Beam-mass model, which is generated with the section property method, is the model simplified effectively. Section property method can provide desired section information by optimization technique. By applying beam-mass model to the crankshaft in the large marine engine, the usefulness of the proposed method was proven.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.223-228
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• 2003

Recently, owing to the deterioration of reconstruction and the construction, much of the construction waste is discharged in our construction field, and the amount of construction waste is rapidly increased. These waste are raised to financial and environmental problems, so the method of reusing waste concretes has been studied and carried out many direction. Especially being want of resources, if waste concrete could be recycled as aggregates for concrete, it will contribute to solve the exhaustion of natural aggregate, in terms of saving resources and protecting environment. This study is that the mechanical properties of concrete with recycled coarse aggregate were investigated for types of mineral admixture and the substitution of recycled coarse aggregate. The result of this study, in case of using mineral admixture, the property of fresh concrete was rised. And the property of harden concrete for the substitution ratio of recycled coarse aggregate was decreased. But the property of concrete with mineral admixture was better than that of concrete used only cement.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.185-189
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• 1999

There has been a considerable attention in Invar alloys because of its low thermal expansion property. A low thermal expansion property of Invar alloys, lower than 10-6 near the room temperature, is attractive for precision machine tools. However, the expansion property of Invar alloys is limited below about 520。K, and mechanical properties are relatively low to apply to machine tools. In order to improve mechanical properties in this alloy, Ti alloy element was added to an invar alloy. Microstructure changes and optimum heat-treatment conditions according to Ti addition were discussed in the Ni38-Mo2-Crl-Fe Invar alloy.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.964-968
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• 2001

The refractory-lined pipe is used to protect the system from high-temperature of the internal flow. The property of the refractory has an effect upon the stress analysis for fluid catalyst cracking(FCC) unit piping design. The equivalent elastic modulus and density considering steel and refractory must be applied in the stress analysis of the system. In the research, the theoretical method to obtain the value of the equivalent property is introduced and then the parametric analysis is carried out to understand the characteristic of the material properties.

• Journal of the Korean Wood Science and Technology
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• 제29권3호
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• pp.68-72
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• 2001

In order to effectively use the waste wood, two types of woodceramics chip tile were made from woodceramics chip, gravel, zeolite and additions. The woodceramics chip was made from branch of apple tree (Malus pumila Mill.) Snow melting property, bending strength and compressive strength of woodceramics chip tile were tested according to the mixing rate of woodceramics chip. Snow melting properties of woodceramics chip tile increased after additions treatment but mechanical properties were reduced significantly after additions treatment. The results indicate that the additions are effective for snow melting property but negative effect on mechanical properties.

• Elastomers and Composites
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• 제53권2호
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• pp.67-74
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• 2018

Magneto-rheological elastomers (MREs) are smart materials in which the inherent stiffness and damping properties can be changed by the influence of an external magnetic field. The magneto-rheological (MR) effect depends on the orientation characteristics of the dispersed magneto-responsible particles (MRPs) in the matrix. In this study, natural rubber (NR) and ethylene propylene diene rubber (EPDM) were blended and used as a matrix of an MRE. EPDM was pre-cured before blending with NR. The Mooney viscosity, curing characteristics, and mechanical properties were analyzed with various pre-curing conditions of EPDM and the NR/EPDM blend. The results show that excellent mechanical properties of the NR/EPDM blend-based MRE were obtained when the pre-curing time of EPDM was 60 min. The aging property of the NR-based MRE was improved by the introduction of pre-cured EPDM. Also, the anisotropic MRE showed a higher MR effect than that of the isotropic MRE.