• 한국초전도ㆍ저온공학회논문지
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• 제9권3호
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• pp.9-12
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• 2007

In this study. we searched for the mechanical and electrical properties of laminated coated conductors with stabilizer tape. Stabilizer tape plays a role for mechanical and electrical stability and environmental protection. Cu material stabilizer was laminated to Ag capping layer on SmBCO conductor layer. This architecture allows the wire to meet operational requirements including the stressless at cryogenic temperature and winding tension as well as mechanical bending requirements including thermal and electrical stability under fault current conditions. First, we have experimentally studied mechanical bonding properties of the laminated Cu stabilizers on SmBCO coated conductors. We have laminated SmBCO coated conductors by continuous dipping soldering process, Second, we have investigated electrical properties of the SmBCO coated conductors with stabilizer lamination. We evaluated bonding properties, peeling strength and critical current for laminated SmBCO coated conductors with Cu stabilizers.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.28-31
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• 2023

This study presents a comprehensive procedure for the low cycle fatigue test of ultrasonically welded (UW) coated conductor (CC) lap-joints. The entire process is examined in detail, from the robust fabrication of the UW REBCO CC joints to the reliability testing under a low number of repeated cycle fatigue conditions. A continuous I_c measurement system enables real-time monitoring of I_c variations throughout the fatigue tests. The study aims to provide a step-by-step procedure that involves joint fabrication, electromechanical property (EMP) tests under uniaxial tension for stress level determination, and subsequent low-cycle fatigue tests. The joints are fabricated using a hybrid method that combines UW with adding In-Sn soldering, achieving a flux-free hybrid welding approach (UW-HW flux-free). The selected conditions for the low cycle fatigue tests include a stress ratio of R=0.1 and a frequency of 0.02 Hz. The results reveal some insights into the fatigue behavior, irreversible changes, and cumulative damage in the CC joints.

• Journal of Welding and Joining
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• 제26권3호
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• pp.30-36
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• 2008

A flip-chip bonding system using IR laser with a wavelength of 1064 nm was developed and associated process parameters were analyzed using Taguchi methods. An infrared laser beam is designed to transmit through a silicon chip and used for transferring laser energy directly to micro-bumps. This process has several advantages: minimized heat affect zone, fast bonding and good reliability in the microchip bonding interface. Approximately 50 % of the irradiated energy can be directly used for bonding the solder bumps with a few seconds of bonding time. A flip-chip with 120 solder bumps was used for this experiment and the composition of the solder bump was Sn3.0Ag0.5Cu. The main processing parameters for IR laser flip-chip bonding were laser power, scanning speed, a spot size and UBM thickness. Taguchi methods were applied for optimizing these four main processing parameters. The optimized bump shape and its shear force were modeled and the experimental results were compared with them. The analysis results indicate that the bump shape and its shear force are dominantly influenced by laser power and scanning speed over a laser spot size. In addition, various effects of processing parameters for IR laser flip-chip bonding are presented and discussed.

• 한국안전학회지
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• 제27권2호
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• pp.7-12
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• 2012

This paper describes electrical fire on electric pad caused by defect of hot wires. We analyzed two type electric pad using by carbon type hot wire and magnetic shielded type hot wire. First, a carbon type hot wires electric pad is virtually impossible to connect hot wire as a method of electrical welding or soldering. In order to connect between hot wires, that has to splice carbon type material connector. If junction of hot wires was occurrence of poor connection on electric pad, it increase contact resistance on this junction point. With increasing contact resistance, junction of hot wires on electric pad generates local heating and finally leads to electrical fire. An electric pad using by a magnetic shielded type hot wire happened local heating on signal wire for sensing temperature-rise caused by applying current for magnetic shielded. With increasing local heating of signal wire, insulated coating of hot wire was melted. Finally the magnetic shielded type hot wire electric pad lead to electrical fire with breakdown between signal wire and hot wire. In this paper, we analyzed shape of damage in hot wire caused by electrical local heating and investigated fire cause on electric pad due to defect of hot wires.

• 한국재료학회지
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• 제22권2호
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• pp.82-85
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• 2012

The effect of the alloy systems Al-Mg alloy and Al-Si alloy in this study on the characteristics of die-casting were investigated using solidification simulation software (MAGMAsoft). Generally, it is well known that the casting characteristics of Al-Mg based alloys, such as the fluidity, feedability and die soldering behaviors, are inferior to those of Al-Si based alloys. However, the simulation results of this study showed that the filling pattern behaviors of both the Al-Mg and Al-Si alloys were found to be very similar, whereas the Al-Mg alloy had higher residual stress and greater distortion as generated due to solidification with a larger amount of volumetric shrinkage compared to the Al-Si alloy. The Al-Mg alloy exhibited very high relative numbers of stress-concentrated regions, especially near the rib areas. Owing to the residual stress and distortion, defects were evident in the Al-Mg alloy in the areas predicted by the simulation. However, there were no visible defects observed in the Al-Si alloy. This suggests that an adequate die temperature and casting process optimization are necessary to control and minimize defects when die casting the Al-Mg alloy. A Tatur test was conducted to observe the shrinkage characteristics of the aluminum alloys. The result showed that hot tearing or hot cracking occurred during the solidification of the Al-Mg alloy due to the large amount of shrinkage.

• 마이크로전자및패키징학회지
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• 제7권2호
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• pp.13-19
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• 2000

금속간 화합물의 두께와 솔더와 금속간 화합물의 계면 거칠기가 Cu pad위의 BGA솔더 조인트의 전단강도에 미치는 영향을 Sn (0. 1.5, 2.5wt.% Cu)와 Sn-40Pb (0, 0.5wt.% Cu) 솔더를 사용하여 알아보았다. 각각의 조성의 솔더를 사용하여 솔더링 반응을 1, 2 ,4분 동안 한 후 전단강도를 측정하였다. Sn솔더에 Cu 첨가는 초기 금속간 화합물의 두께를 증가시키는 결과를 가져오는 반면 Sn-40Pb 솔더의 경우에는 주로 금속간 화합물/솔더의 계면거칠기의 감소를 가져오게 된다. 최대 전단 강도값을 나타내는 금속간 화합물의 임계두께는 솔더의 물질에 따라 변하게 되는데, 본 실험에서는 Sn-Cu솔더의 경우에는 ~2.3 $\mu\textrm{m}$, Sn-Pb-Cu에서는 ~ 1.2 $\mu\textrm{m}$ 정도로 측정되었다. 금속간 화합물의 임계두께는 금속간 화합물/솔더의 계면이 더욱 거칠어질수록 증가하는 것으로 나타났다. 이는 파단면 관찰에서 나타난 초기의 솔더내에서의 파괴가 금속간 화합물이 임계두께 이상으로 성장함에 금속간 화합물/솔더의 계면으로 이동하는 결과와 일치한다.

• 마이크로전자및패키징학회지
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• 제25권2호
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• pp.1-8
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• 2018

In the soldering industry, a variety of lead-free solders have been developed as a part of restricting lead in electronic packaging. Sn-Ag-Cu (SAC) lead-free solder is regarded as one of the most superior candidates, owing to its low melting point and high solderability as well as the mechanical property. On the other hand, the mechanical property of SAC solder is directly influenced by intermetallic compounds (IMCs) in the solder joint. Although IMCs in SAC solder play an important role in bonding solder joints and impart strength to the surrounding solder matrix, a large amount of IMCs may cause poor strength, due to their brittle nature. In other words, the mechanical properties of SAC solder are of some concern because of the formation of large and brittle IMCs. As the IMCs grow, they may cause poor device performance, resulting in the failure of the electronic device. Therefore, new solder technologies which can control the IMC growth are necessary to address these issues satisfactorily. There are an advanced nanotechnology for microstructural refinement that lead to improve mechanical properties of solder alloys with nanoparticle additions, which are defined as nano-reinforced solders. These nano-reinforced solders increase the mechanical strength of the solder due to the dispersion hardening as well as solderability of the solder. This paper introduces the nano-reinforced solders, including its principles, types, and various properties.

• Journal of Welding and Joining
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• 제25권2호
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• pp.82-88
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• 2007

Sn-3.0Ag-0.5Cu lead fee solder was generally utilized in electronics assemblies. But it is insufficient to research about activation energy(Q) that is applying to evaluate the solder joint reliability of environmental friendly electronics assemblies. Therefore this study investigated Q values which are needed to IMC formation and growth of Sn-3.0Ag-0.5Cu/Cu and Sn-40pb/Cu solder joints during aging treatment. We bonded Sn-3.0Ag-0.5Cu and Sn-40Pb solders on FR-4 PCB with Cu pad$(t=80{\mu}m)$. After reflow soldering, to observe the IMC formation and growth of the solder joints, test specimens were aged at 70, 150 and $170^{\circ}C$ for 1, 2, 5, 20, 60, 240, 960, 15840, 28800 and 43200 min, respectively. SEM and EDS were utilized to analysis the IMCS. From these results, we measured the total IMC$(Cu_6Sn_5+Cu_3Sn)$ thickness of Sn-3.0Ag-0.5Cu/Cu and Sn-40Pb/Cu interface, and then obtained Q values for the IMC$(Cu_6Sn_5,\;Cu_3Sn)$ growth of the solder joints.

• 마이크로전자및패키징학회지
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• 제11권3호
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• pp.47-53
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• 2004

공정 Au-20Sn 솔더합금을 솔더링 시간과 온도를 달리하여 Ni위에서 솔더링하였다. 주사전자현미경 (SEM)을 사용하여 계면에 생성된 IMC의 조성, 상, 모양에 대해 조사하였다. 계면에는 $(Au,Ni)_3Sn_2$와 $(Au,Ni)_3Sn_2$의 두 가지 IMC가 생성되었다. 그 중 첫 번째 생성된 IMC인 $(Au,Ni)_3Sn_2$상은 솔더링 온도에 따라 모양의 변화가 관찰되었다. 이러한 모양의 변화로 인한 확산통로수의 변화는 모든 솔더링 온도에서 거의 비슷한 IMC 두께를 가지도록 한다. IMC, $(Au,Ni)_3Sn_2$상의 모양변화는 온도 증가에 의한 생성엔탈피의 감소 때문인데, 이는 Jackson's parameter로써 잘 설명될 수 있다.

• 대한치과보철학회지
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• 제34권1호
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• pp.143-150
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• 1996

The purpose of this study was to evaluate the tensile strength of solder joint between gold alloy and nickel-chromium alloy. The specimens were made with type III gold alloys and Ni-Cr-Be alloy and Degular Lot 2 solder. Eighteen paired specimens were made, and subdivided into three groups. Group I specimens were gold alloy-gold alloy combination, Group II specimens were gold alloy-Ni-Cr alloy combination, Group III specimens were Ni-Cr alloy-Ni-Cr alloy combination. Solder block were made with solder investment(Degussa A,G, Germany) and stored in room temperature for 24 hours. To reduce the formation of metallic oxide and increase wetting properties, flux was used before preheating and soldering procedure. The specimens were preheated at $650^{\circ}C$ and flux were applied again and gas-oxygen torch was used to solder the specimen. All soldered specimens were subjected to a tensile force in the Instron universal testing machine : the crosshead speed was 1 mm/mim. Tensile strength values of three soldered joint groups were 1. Gold alloy-Gold alloy solder joint : $$48.8kg/mm^2$$ 2. Gold alloy-Ni-Cr alloy solder joint : $$30.9kg/mm^2$$ 3. Ni-Cr alloy-Ni-Cr alloy solder joint : $$31.8kg/mm^2$$ The microscopic examination of fracture site showed cohesive and combination fracture modes in gold alloy specimens, but showed all adhesive fracture modes in Ni-Cr alloy containing specimens.