• Journal of Welding and Joining
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• v.33 no.3
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• pp.47-53
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• 2015

By the trends of electronic package to be more integrative, the fine Cu trace pitch of organic PCB is required to be a robust design. In this study, the short circuit failure mechanism of PCB with a Cl element under the Temperature humidity bias test ($85^{\circ}C$/85%RH/3.5V) was examined by micro-structural study. A focused ion beam (FIB) and an electron probe micro analysis (EPMA) were used to polish the cross sections to reveal details of the microstructure of the failure mode. It is found that $CuCl_x$ were formed and grown on Cu trace during the $170^{\circ}C$/3hrs and that $CuCl_x$ was decomposed into Cu dendrite and $Cl_2$ gas during the $85^{\circ}C$/85%RH/3.5V. It is suggested that Cu dendrites formed on Cu trace lead to a short circuit failure between a pair of Cu traces.

• Journal of Welding and Joining
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• v.29 no.1
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• pp.41-45
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• 2011

SnAgCu lead-free solder alloy is considered as the best alternative to eutectic tin-lead solder. However, the detailed material properties of SnAgCu solder are not available in public. Hence, this paper presents an estimation of mechanical properties of SnAgCu lead-free solder. In particular, the weight percent of Ag was varied as 1.0wt%, 2.5wt%, 3.0wt%, and 4.5wt% in order to estimate the effect of Ag in the Sn-xAg-0.5Cu ternary alloy system. For this purpose, four types of SnAgCu bars were first molded by casting and then standard specimens were cut out of molded bars. Micro-Vickers hardness, tensile tests were finally performed to estimate the variations in mechanical properties according to the weight percent of Ag. Test results reveal that the higher the weight percent of Ag is, the higher the hardness, yield strength, and ultimate tensile strength become. More material properties will be further investigated in the future work.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.81-88
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• 2014

As the industrial technology has been developed, a dissimilar welding has been received huge attention in various engineering fields. To understand the mechanical properties and possibility of applications of dissimilar metals joining, the laser welding of Cu and Ni dissimilar metals was studied in this paper. Cu and Ni have differences in materials properties, and Cu and Ni make no intermetallic compounds according to typical binary phase of Cu and Ni system. In this study, lap welds of Cu and Ni dissimilar metals using single-mode fiber laser with high welding speed were tried, and mechanical properties of the welds zone were evaluated using a Vickers hardness test and a tensile shear test. To recognize the relation between hardness and tensile shear load, weld fusion zone of interface weld area were observed. And it was confirmed that the ultra-high welding speed could make good weld beads and higher hardness parts had higher tensile shear load under the all conditions.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.77-81
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• 2013

We have investigated thermal stability of the mechanical and thermal conductive properties of Cu/STS/Cu 3 layered clad metal lead frame material for a LED device package at different temperatures ranging from RT to $200^{\circ}C$. The fabricated Cu/STS/Cu clad metal has a good thermal stability for the mechanical tensile strength and thermal conductivity of the over 50 $Kg/mm^2$ to the $150^{\circ}C$ and 270 $W/m{\cdot}K$ to the $200^{\circ}C$, respectively. This clad metal lead frame material at a high temperature of $150^{\circ}C$ shows a reinforced mechanical tensile strength by 1.5 times to conventional pure copper lead frame materials and also a comparable thermal conductivity to typical copper alloy lead frame materials.

• Journal of Welding and Joining
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• v.30 no.3
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• pp.32-37
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• 2012

Lead frame which has a high thermal conductivity and high mechanical strength is one of core technology for ultra-thin electronics such as LED lead frames, memory devices of semiconductors, smart phone, PDA, tablet PC, notebook PC etc. In this paper, we fabricated a Cu/STS/Cu 3-layered clad metal for lead frame packaging materials and characterized the mechanical properties and thermal conductive properties of the clad metal lead frame material. The clad metal lead frame material has a comparable thermal conductivity to typical copper alloy lead frame materials and has a reinforced mechanical tensile strength by 1.6 times to typical pure copper lead frame materials. The thermal conductivity and mechanical tensile strength of the Cu/STS/Cu clad metal are 284.35 W/m K and $52.78kg/mm^2$, respectively.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.79-89
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• 1999

The study was carried out to examine in more detail metallurgical and mechanical properties of brazed joints of diamond cutting wheel. In this work, shank(mild steel) and sintered bronze-base tips were brazed with three different filler materials(W-40, BAgl and BAg3S). The machine used in this work was a high frequency induction brazing equipment. The joint thickness, porosities and microstructure of brazed joints with brazing variables(brazing temperature, holding time) were evaluated with OLM, SEM, EDS and XRD. Bending(torque) test was also performed to evaluate strength of brazed joints. Further wetting test was performed in a vacuum furnace in order to evaluate the wettability of filler metals on base metals9shank and tips). The brazing temperature had a strong influence on the joint strength and the optimum brazing temperature range was about $700~850^{\circ}C$ for the bronze/steel combinations. The strength of the brazed joint was found to be influenced by the three factors : degree of reaction region, porosity content, joint thickness. The reaction region was formed in the bronze-base tip adjacent to the joint. The reaction region resulted in a bad influence on the strength due to the formation of Cu5.6Sn, CuZn4, $\beta(CuZn)$ and CdAg, etc. Porosities increased as brazing variables(brazing temperature, holding time) increased, and the brazed joints with porosities of less than about 3-5% had an optimum strength for the bronze-base tip.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.55-61
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• 2010

An impact bending test method was used to evaluate the reliability for the solder joint of lead-free solder ball. In order to standardize the test method, the four point impact bending test was applied under the conditions of various frequencies and amounts of +/-amplitude respectively. Effects on the results were analysed. The optimum condition for impact bending test achieved in this study was the frequency of 10 Hz, and the amplitude of (+12/-1)~(+15/-1). 3 kinds of surface finishes Cu-OSP (Organic Solderability Preservative), ENIG (Electroless Nickel Immersion Gold), and ENEPIG (Electroless Nickel, Electroless Palladium, Immersion Gold) were used. Fracture surface showed that cracks were initiated and fractured along the intermetallic layer in the case of surface finishes of Cu-OSP and ENIG, while in the case of ENEPIG the cracks were initiated and propagated in the solder region.

• Journal of Welding and Joining
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• v.5 no.4
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• pp.47-53
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• 1987

The purpose of this study is to reexamine our test method in the light ofstatistical methods for data interpretation. Our trial to apply Plackett-Burman statistical model in multifactorial welding experiments shows that is saves much time and cost and extracts very accurate results. In this study, the parametric effects of bead shape on pulse MIG process in Cu-Ni alloy are investigated for verifying our trial.

• Journal of Welding and Joining
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• v.8 no.3
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• pp.31-38
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• 1990

The bonding mechanism and bond strength were investigated for the cold pressure welding of Al to Al, Cu to Cu and Al to Cu by upsetting. A phenomenon of bonding betweenthe metallic components has been observed by a scanning electron microscope and metallurgical microscope. A modified equation for bond strength with respect to the reduction of height shows reasonably a good agreement with the experimental data. When the values of the hardening factor and threshold deformation for the given materials could be determined, the theoretical bond strength can be calculated.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.168-168
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• 2015

플라즈마를 이용하여 PET표면에 나노구조를 형성시킨 후 무전해 도금에 의해 구리를 코팅함으로써 플랙서블한 Cu/PET 기판을 제조하였다. 플라즈마 에칭시간을 달리하여 나노구조의 크기와 모양을 변화시켰으며 나노구조의 크기와 모양의 변화에 따른 Cu와 PET의 접합강도와 피로특성을 평가하였다.