• Journal of Welding and Joining
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• v.22 no.4
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• pp.35-42
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• 2004

Contact tips are required to have a higher resistance to wear and thus to have an extended life time under the advanced GMAW welding process. Several requirements have been specified and employed by domestic industries for selecting their tips for such a purpose. However no attempt has been made to justify their requirements based on the experimental data of wear resistance or life time of contact tips. In this study, five different contact tips with three different compositions were employed for actual GMA welding up to 4 hours and were evaluated their wear resistance by measuring in every one hour the area of enlarged hole at the exit side. Experimental results clearly showed that the Cr-containing tips strengthened by precipitation hardening have much better resistance to wear than those made by work hardening. It was further noticed that Cr is an excellent alloying element for improving the wear resistance of contact tips only when it is in an properly aged condition. Initial hardness may play some role in the early stage of wear but not in the later stage of welding because the microstructure of tip changes significantly by the prolonged exposure to welding arc heat. Based on these results, critical review has been made on the current requirements employed by domestic industries. Of importance is that a new guideline has been confirmed to be more reasonable.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.6
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• pp.90-96
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• 2011

In this study, the characteristic of fractured portion and shape on solder joints were investigated according to the thermal shock test for Automotive Application Component using Sn-3.0Ag-0.5Cu solder, which has a outstanding property as Lead-free solder. The value of pull and shear strength was decreased in principle after 432 cycles thermal shock test. In addition, fracture mode was verified by using EDS and SEM to observe fractured shape on the solder joints before and after thermal shock. In before thermal shock test, the fracture mode revealed typically solder layer's fracture mode. In after thermal shock test, we identified multiple fracture mode of the ductile and brittle fracture. Even though same composition of solder was used to experimental for estimating. the fracture mode varied on the fracture portion's height and the directional angles of shear strength. In conclusion, we identified that mechanical strength was affected on the solder layer's fracture mode.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.120-122
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• 2003

We jointed Bi(Pb)-Sr-Ca-Cu-O multifilament tapes and evaluated their electrical properties. In order to improve connectivity of multifilarnents, single-filament tape was inserted between two multifilament tapes or multifilament was stepped by mechanical remove. The critical current ratio (CCR) and n-value of the jointed tapes were evaluated as a function of uniaxial pressure. It was observed that CCR and n-value were 24.8-29.0% and 2.5-2.8 for lap-jointed tape. On the other hand, the corresponding values were improved to 51.8-61.9% and 2.9-5.1 for three stepped jointed tape, and 63.4-67.9% and 3.4-4.2 for double MSM lap-jointed tape, respectively. These improvements are to be due to better interconnection between filaments of two tapes.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.37-42
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• 2011

In this paper, novel carbon nanotube (CNT)-filled Solderable electrically conductive adhesive (ECA) and joining process have been developed. To investigate the bonding characteristics of CNT-filled Solderable ECA, three types of Solderable ECAs with different CNT weight percent (0, 0.1, 1wt%) were formulated. For a joining process, the quad flat package (QFP) chip was used. The QFP chip had a size of $14{\times}14{\times}2.7$ mm and a 1 mm lead pitch. The test board had a Cu daisy-chained pattern with 18 ${\mu}m$ thick. After the bonding process, the bonding characteristics such as morphology of conduction path, electrical resistance and pull strength were measured for each formulated ECAs. As a result, the electrical and mechanical bonding characteristics for a QFP joints using CNT-filled ECA were improved about 10% compared to those of QFP joints using ECA without CNT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.262-263
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• 2005

For mechanical and electrical stability and environment protection, Cu and stainless steel stabilizer is laminated to Ag layer to produce a composite neutral-axis(N-A) architecture in which the YBCO layer is centered between the oxide buffered metallic substrate and stabilizer strip lamination. this architecture allows the wire to meet operational requirements including stresses at cryogenic temperature, winding tensions, mechanical bending requirements thermal and electrical stability under fault conditions. we have experimentally studied mechanical properties of laminated stainless steel stabilizer on YBCO coated conductors. we have laminated YBCO coated conductors by continuous dipping soldering process. we have investigated lamination interface between solder and stabilizer, YBCO coated conductor. we evaluated bonding properties tensile / shear bonding strength, peeling strength laminated YBCO coated conductors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.114-115
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• 2006

반도체 기술이 초고집적화 되어감에 따라 공정에서 선폭이 줄어들고, 박막을 다층으로 제조하는 것이 중요하게 되었다. 이와 같은 제조 공정 하에서는 Si 기판과 금속 박막간의 확산이 커다란 문제로 부각되어 왔다. 특히 Cu는 높은 확산성에 의하여 Si 기판과 접합에서 많은 확산에 의한 문제가 발생하게 되며. 또한 선폭이 줄어듦에 따라 고열이 발생하여 실리콘으로 spiking이 발생하게 된다. 이를 방지하기 위하여 우리는 3개의 화합물로 구성된 Tungsten-Carbon-Nitrogen (W-C-N) 확산방지막을 사용하였다. 실험은 물리적 기상 증착법 (PVD)으로 질소비율을 변화하며 확산방지막을 증착하였고, 이를 여러 온도에서 열처리하여 X-ray Diffraction 분석을 하였다.

• Journal of Welding and Joining
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• v.16 no.3
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• pp.157-166
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• 1998

Recently as environmental pollution caused by Pb has posed a serious threat to the global environment, the trend to regulate the usage of Pb in electronic industry is one the rise. Currently, the solder alloy with high Pb content, Sn-37%Pb, is utilized in the electronic assembly therefore, the objective of this study is to develop an alternative solder alloy for the existing Sn-37%Pb solder alloy. First thing, this work choosed Sn-5%Pb-1.5%Ag, Sn-5%Pb-1.5%Ag-x%Bi(x=1~5%) for candidate solder alloys, and examined their properties such as melting range, wettability, microhardness, tensile property, oxidation behavior and microstructure. Wettability was on the same level of Sn-37%Pb. Dissolution of Pb ion in Sn-5%Pb solder was 0.46ppm. This solder alloy revealed cellular dendrite microstructure $\beta$-Sn matrix, Pb-rich phase, Ag/Sn, and Cu/Sn Intermetallic compounds. The range of solidification temperature was within 3$0^{\circ}C$. Also these alloy displayed higher tensile strength and lower elongation than Sn-37%Pb. The resistance of oxidation in Sn-5%Pb-1.5%Ag solder alloy was superior to that of Sn-37%Pb solder alloy. But that of Sn-5%Pb-1.5%Ag-5%Bi solder alloy was equal to that of Sn-37%Pb solder alloy.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.77-83
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• 2013

3D packaging technology using TSV (Through Silicon Via)has been studied in the recent years to achieve higher performance, lower power consumption and smaller package size because electrical line is shorter electrical resistivity than any other packaging technology. To stack TSV chips vertically, reliable and robust bonding technology is required because mechanical stress and thermal stress cause fracture during the bonding process. Cu pillar/solder ${\mu}$-bump bonding process is usually to interconnect TSV chips vertically although it has weak shape to mechanical stress and thermal stress. In this study, we suggest Insert-Bump (ISB) bonding process newly to stack TSV chips. Through experiments, we tried to find optimal bonding conditions such as bonding temperature and bonding pressure. After ISB bonding, we observed microstructure of bump joint by SEM and then evaluated properties of bump joint by die shear test.

• Korean Journal of Materials Research
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• v.19 no.6
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• pp.337-343
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• 2009

In this study, we optimized Pb-free Sn/Ni plating thickness and conditions were optimized to counteract the environmental regulations, such as RoHS and ELV(End-of Life Vehicles). The $B_{10}$ life verification method was also suggested to have been successful when used with the accelerated life test(ALT) for assessing Pb-free solder joint life of piezoelectric (PZT) ceramic resonator. In order to evaluate the solder joint life, a modified Norris-Landzberg equation and a Coffin-Manson equation were utilized. Test vehicles that were composed of 2520 PZT ceramic resonator on FR-4 PCB with Sn-3.0Ag-0.5Cu for ALT were manufactured as well. Thermal shock test was conducted with 1,500 cycles from $(-40{\pm}2)^{\circ}C$ to $(120{\pm}2)^{\circ}C$, and 30 minutes dwell time at each temperature, respectively. It was discovered that the thermal shock test is a very useful method in introducing the CTE mismatch caused by thermo-mechanical stress at the solder joints. The resonance frequency of test components was measured and observed the microsection views were also observed to confirm the crack generation of the solder joints.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.1-7
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• 2021

A computer simulation was performed to study the effectiveness of temperature on the type of laser heat source in the context of the heterogeneous welding of aluminum and copper materials. Three different types of heat sources were used in the computer simulation: 1) Single Beam Straight Scan, 2) Single Beam Wobble Scan, and 3) Dual Beam Straight Scan. Among these sources, dual beam straight scan was found to be the most effective from the viewpoint of heat source control. Because the difference between the melting temperatures of copper and aluminum is approximately 400℃, a clear separation of heating temperature was required, and the dual beam straight scan provided superior controllability in this regard. When using the dual beam, the temperature of the 90:10 split was considerably easier to control than that of the 50:50 split. The optimal offset was calculated to be 4 mm off to the copper side, where the melting temperature and thermal conductivity were higher. In this manner, computer simulation was effectively used for determining the optimal laser beam hear source control without performing an actual laser welding experiment.