• 대한인간공학회지
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• 제29권6호
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• pp.943-949
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• 2010

When PCB soldering is performed with microscope due to the electronic components' microminiaturization, workers' awkward upper body postures and difficulties being in focus among lens, object and eyes are one of reasons for productivity decline. The object of this study is to investigate the level of difficulties of work and the extent of productivity improvement by changing work interfaces from the work using microscope to the work using LCD monitor. Independent variables was usage of microscope and image system and dependent variables were upper body segments including neck, shoulder, back, and waist, task convenience and eye fatigue. The Visual Analogue Scale (10cm) was used for questionnaire and one way ANOVA (two levels) and two sample t-test were conducted. In addition, RULA rating was conducted for working postures. The result showed that interface changes of LCD monitor, suggested by productivity comparison per one Man Hour, highly contributed to work convenience and productivity improvement.

• 대한치과기공학회지
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• 제30권1호
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• pp.131-139
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• 2008

It's very important to find the most appropriate adhesion technique available, taking into consideration factors such as biocompatibility, non-corrosiveness, mechanical stability, etc. Laser welding is the best choice you can make because from a mechanical viewpoint, a laser welded surface has better particle structure than does a casted particle structure. Furthermore, it requires no additional material and the same metal alloy which is used when casting can be used. Therefore, the resulting mixture will consist of a single alloy, instead of utilizing different alloy combinations. Another benefit is the low economic cost. The most beneficial aspects of laser welding is that it is biologicallly friendlly, doesn't require soldering, can fuse different metal alloys together, and can weld on heat-sensitive spots(E.g. around resin or ceramic). A consistent strong pulse is possible. This technique is capable of welding on master models and creates accurate welds. It is capable of due to its stronger, non-corrosive microscope, which allows 25times magnification during the soldering process. This is possible because of its high stability from the tiny particle structure.

• 한국재료학회지
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• 제31권11호
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• pp.601-607
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• 2021

Laser cladding a surface treatment process that grants superior characteristics such as toughness, hardness, and corrosion resistance to the surface, and rebuilds cracked molds; as such, it can be a strong tool to prolong service life of mold steel. Furthermore, compared with the other similar coating processes - thermal spray, etc., laser cladding provides superior bonding strength and precision coating on a local area. In this study, surface characteristics are studied after laser cladding of low carbon steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), known for its high hardness and excellent corrosion resistance. A diode laser with wavelength of 900-1070 nm is adopted as laser source under argon atmosphere; electrical power for the laser cladding process is 5, 6, and 10 kW. Fundamental surface characteristics such as crossectional microstructure and hardness profile are observed and measured, and special evaluation, such as a soldering test with molten ALDC12 alloy, is conducted to investigate the corrosion resistance characteristics. As a result of the die-soldering test by immersion of low carbon alloy steel in ALDC12 molten metal, the clad layer's soldering thickness decreases.

• 한국초전도ㆍ저온공학회논문지
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• 제10권1호
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• pp.24-27
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• 2008

For the development of superconducting fault current limiters(SFCLs) having large current capacity, we fabricated an SFCL element that consists of Bi-2212 superconductor and Cu-Ni alloy tubes. First, Ag was plated on the surface of the Bi-2212 for the enhancement of soldering process. On the Ag-plated Bi-2212 tube, a Cu-Ni alloy tube was soldered using optimized solders and soldering conditions. The BSCCO/Cu-Ni composite was processed mechanically to have a helical shape for the improvement of the SFCL characteristics. The total current path of the SFCL element was 1330 mm long with 12 turns, and had critical current of 340 A at 77 K. Finally, we carried out the fault test using the fabricated SFCL element. It showed successful current limiting performance under the fault condition of 50 $V_{rms}$ and 5.5 kA. From the results, the rated voltage of the SFCL element was decided to be 0.4 V/cm, and the power capacity was 12 kVA at 77 K. The fabrication process of the SFCL and the fault test results will be presented.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.791-797
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• 2002

This paper introduces the partial melting process for solder application and characterization of its feasibility using Sn-Ag, and Sn-Cu solder alloys. ill order to show that the liquid phase in the semi-liquid state maintains the similar wettability as single-phase liquid, the wetting balance tests are conducted with varying temperatures and compositions. Also, as a new soldering technology, the microstructural and mechanical test were investigated. The results from this research indicate that the partial melting can yield satisfactory sider joints as long as the liquid phase acquires sufficient chemical activity. At a condition where the partial melting is effective, a direct correlation between the wettability and the surface tension is found to exist.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4065-4071
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• 2014

PV셀과 리본의 솔더링 공정에서 열풍온도에 따른 $200{\mu}m$ 두께의 PV셀의 온도분포와 변형량의 해석 결과는 실험 측정치와 거의 일치함을 알 수 있었다. 또한 전기효율은 설정온도 $390^{\circ}C$로 PV셀을 솔더링한 모듈에서 가장 좋은 결과가 나타났다. 열풍온도를 $350^{\circ}C$로 설정하고 $150{\mu}m$ 두께의 PV셀을 솔더링 해석한 결과, 최대 변형량이 약 5.9mm로서 상당히 큰 값임을 확인할 수 있었으며, 열풍온도를 보다 낮은 온도로 설정해야 변형량이 감소하고 전기효율이 향상될 것을 예측하였다.

• Current Photovoltaic Research
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• 제7권3호
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• pp.65-70
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• 2019

As a demand of higher power photovoltaic modules, shingled, multi-busbar, half-cell, and bifacial techniques are developed. Multi-busbar module has advantage for large amount of light havesting. And, half-cell is high power module for reducing resistive losses and higher shade tolerance. Recently, researches on multi-busbar is focused on reliability according to adhesion and intermetallic compound between Sn-Pb solder and Ag electrode. And half-cell module is researched to comparing with full-sized cell module for structure difference. In this study, we investigated the factors affecting to efficiency and adhesion of multi-wires half-cell module according to wire thickness, solder thickness, and flux. The results of solar simulator and peel test was that peel strength and efficiency of soldered cell is not related. But samples with flux including high solid material showed high efficiency. The results of FE-SEM and EDX line scan on cross-section between wire and Ag electrode for different flux showed thickness of solder joint between wire and Ag electrode is increasing through solid material increasing. Flux including high solid material would affect to solder behavior on Ag electrode. Higher solid material occurred lower growth of IMC layer because solder permeate to sider of wire ribbon than Ag electrode. And it increased fill factor for high efficiency. In soldering process, amount of solid material in flux and solder thickness are the factor related with characteristic of soldered photovoltaic cell.

• 실천공학교육논문지
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• 제16권2호
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• pp.179-184
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• 2024

인쇄회로기판(PCB)은 전자 제품 생산에 널리 적용되는 요소부품으로 지속적으로 양적인 성장은 물론 집적도와 같은 질적인 발전도 묵과할 수 없다. 제조현장에서 보편적으로 웨이브 솔더링 장비가 사용되고 있으나 선행 연구 및 시제품 개발 단계에서는 각 PCB 제원에 맞는 전용 장비 환경을 구성할 수 없고, 범용의 고정 장비 환경에서 정해진 시간 내에 장비의 설정 조건만 변경하여 다양한 제품 군을 생산할 수밖에 없는 것이 일반적이다. 본 연구에서는 위와 같이 제한된 환경 내에서 최적의 공정 조건을 선택할 수 있도록 PCB 팔레트 도입 사례를 소개한다. 또한 현재 범용 장비에서 생산 가능 여부를 미리 판단할 수 있는 판별식을 제시하여 범용 웨이브 솔더링 장비 환경의 한계로 인해 발생할 수 있는 문제점을 사전에 파악하고 대응하도록 하고 궁극적으로 개발기간 단축 및 생산성 향상을 기대할 수 있도록 한다.

• 대한기계학회논문집A
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• 제28권6호
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• pp.709-716
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• 2004

In order to prevent the interface delamination of an plastic IC package in the infrared (IR) soldering process, we tried to reduce stress by parameterization, sensitivity analysis and unconstraint optimization. The design variables of dimensions and material properties are determined among all the possible variables from the parametric study. Their optimized values are determined by applying the unconstraint optimization to the parameterized IC package. The maximum von-Mises stress value decreases greatly by optimum design.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.357-369
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• 2004

The purposes of the paper are to analyze the fracture phenomenon by delamination and cracking when the encapsulant of plastic IC package with polyimide coating shows viscoelastic behavior under hygrothermal loading in the IR soldering process and to suggest more reliable design conditions by the approaches of stress analysis and fracture mechanics. The model is the plastic SOJ package with the polyimide coating surrounding chip and dimpled diepad. On the package without cracks, the optimum position and thickness of polyimide coating to decrease the maximum differences of strains at the bonding surfaces of parts of the package are studied. For the model delaminated fully between the chip and the dimpled diepad, C(t)-integral values are calculated for the various design variables. Finally, the optimal values of design variables to depress the delamination and crack growth in the plastic IC package are obtained.