• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.601-608
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• 2008

Joints of single-layer latticed domes show various flexural behaviors according to their shapes and connecting methods. Ball joints are relatively easy to apply and build while their rigidities are relatively small and have disadvantage in long span. Welded joints have many advantages in rigidity, internal force and long span. However few experimental studies have been performed. In this paper, improved welded joint for the single layer latticed domes was proposed through both analytical and experimental analyses. Length of inserted plates, thickness of inserted plates and hole of sub steel pipes were selected as parameters for experimental comparisons and defining the effects of the selected variables.

• Journal of Korean Association for Spatial Structures
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• v.7 no.6
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• pp.61-68
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• 2007

The hole for the insertion of the pin in the shank is exist at ball joint connection of the space frame. It brings about the brittle fracture caused by stress concentration. Consequently it cannot expect the deformation performance or energy absorption performance from ball joint connection. In this study we developed a new connection details which will increase the plastic deformation performance at ball joint connection and can absorb the error in construction, which expect the plastic deformation performance at the reduced shank without brittle fracture at the screw of bolt and pin. Also it's capacity is verified by the performance in numerical analysis and test. We confirmed bolt's plastic deformantion performance through controled shank and pin's area.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.219-223
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• 2002

전자부품의 고성능화 고집적화를 위한 표면실장기술의 발전과 환경과 건강에 대한 관심의 증가로 땜납 중의 납의 독성과 그에 따른 납 사용 규제 움직임과 선진국의 법규제에 대응 하여 무연 땜납이 개발되고 있다. 본 연구는 이러한 배경에서 무연 땜납용 볼에 관한 기술정보의 유용성의 제고와 객관적인 비교평가를 위한 표준을 제시하는데 그 목적이 있다. 본 연구에서는 납점용 볼의 표준화 현황을 조사하고, 기업을 대상으로 설문조사를 실시하여 납땜용 볼에 대한 인식과 표준화 현황을 조사하였다. 또, 기존에 납땜용 볼에 관하여 발표되었던 자료들을 조사하여, 유연.무연 납땜용 볼의 품질특성과 그 평가방법을 비교하여 연구하였다. 무연 납땜용 볼은 외관이 거칠고, 융점과 표면장력의 차이로 인하여 젖음성이 떨어지며, 리플로우 조건에 따라 접합부의 높이에 변화가 있으며, 접합강도는 높아지는 특성을 보였으며 접합부의 신뢰성에서도 유연 납땜용 볼과는 많은 차이를 보였다. 이런 무연 땜납의 특성을 감안하여, 몇 가지 품질특성별 평가방법 및 기준을 제시하였다.

• Journal of Korean Association for Spatial Structures
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• v.7 no.6
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• pp.53-60
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• 2007

The hole for the insertion of the pin in the shank is exist at ball joint connection of the space frame. It brings about the brittle fracture caused by stress concentration. Consequently it cannot expect the deformation performance or energy absorption performance from ball joint connection. In this study we developed a new connection details which will increase the plastic deformation performance at ball joint connection and can absorb the error in construction, which expect the plastic deformation performance at the reduced shank without brittle fracture at the screw of bolt and pin. Also it's capacity is verified by the performance in numerical analysis and test. We confirmed bolt's plastic deformantion performance through controled shank and pin's area.

• Proceedings of the KWS Conference
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• 2010.05a
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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.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.69-74
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• 2015

With difficulties during the cleaning of reflow flux residues due to the decrease of the part size and interconnection pitch in the advanced electronic devices, the need for the no-clean solder paste is increasing. In this study, an epoxy curable solder paste was made with SAC305 solder powder and the curable flux of which the main ingredient is epoxy resin and its reflow solderability, flux residue corrosivity and solder joint mechanical properties was investigated with comparison to the commercial rosin type solder paste. The fillet shape of the cured product around the reflowed solder joint revealed that the curing reaction occurred following the fluxing reaction and solder joint formation. The copper plate solderability test result also revealed that the wettability of the epoxy curable solder paste was comparable to those of the commercial rosin type solder pastes. In the highly accelerated temperature and humidity test, the cured product residue of the curable solder paste showed no corrosion of copper plate. From FT-IR analysis, it was considered to be resulted from the formation of tight bond through epoxy curing reaction. Ball shear, ball pull and die shear tests revealed that the adhesive bonding was formed with the solder surface and the increase of die shear strength of about 15~40% was achieved. It was considered that the epoxy curable solder paste could contribute to the improvement of the package reliability as well as the removal of the flux residue cleaning process.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.125-133
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• 2014

In this study, experimental research was carried out to investigate the seismic and structural performance of precast concrete exterior beam-column joints using bolt type connection and prestressing method. A total of five full-scale exterior beam-column joints were constructed and tested under reversed cyclic loading, controlled by displacement. Results of the test are as follows: Energy dissipation capacity and pinching phenomenon of PC beam-column joints showed disadvantageous behavior compared to RC beam-column joints. However, drift capacity of the PC joint was excellent. Also, yield mechanism concentrated on embedded nuts was suitable as an exterior beam-column joint of lateral load resistance frame. Additional application of prestressing method was also very effective to control excessive pinching and cracking in the joint region, and thus improved an overall seismic performance of the PC joint.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.43-48
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• 2008

The object of this paper is to evaluate on constructability of modular steel frame with the hollow structural steel section to LEB C-shape. A modular building is built with factory-manufacture and site-construction. The advantage of a Modular building presents that enhanced building quality, shortened construction period and easy at an expansion and enlargement for buildings but also has demerits such as size restriction of the modular units according to the Road Traffic Law and Inflexibility of the unit composition. So in this study we use light-weighted structure members with bolted joint for easy Knock-down and traffic, also we evaluated the constructability of this bolted joints type modular buildings.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.2
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• pp.43-55
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• 1995

The turbulent flow around the strut mounted on the plate is studied numerically. The main objective of this paper is to validate the numerical scheme by the comparison of the computed results with the measured one, especially, to investigate the applicability of the Baldwin-Lomax(B-L) model to the juncture flow. Computations are made by solving Reynolds-averaged wavier-Stokes equation with MAC method. The computed results are compared with experimental data of Dickinson, collected in the wind tunnel at DTRC. Comparisons show good agreements generally except at the region of wake and very near the juncture. Reynolds stress model seems to be required to improve the accuracy applicable to the juncture flow in spite of the many simplification of the turbulence modelling in B-L model.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.59-71
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• 2012

Results of the analysis of the structural behavior of axially loaded nodes in freeform structure were not fully understood due to certain difficulties, including the application of various welding and bolting types. In this study, a node of single layered freeform structure was tested to determine its structural behavior when subjected to axial loads. The tests were classified into node ball tests to evaluate the center of the node subjected to cyclic and monotonic loading. The node part tests were also conducted to evaluate the whole node subjected to monotonic loading. The test showed that the node ball is safe with the tensile force, but the node ball needs to increase its strength with the node loaded compressive force due to the additional bending moment of the node ball's asymmetric form.