• Proceedings of the KWS Conference
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• 2005.11a
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• pp.231-233
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• 2005

Laser have been utilized as a heat source for the soldering of electronic components for the their capability of localized heating and faster heating rate. Laser soldering process, especially the diode laser soldering of BGA solderball was investigated. In this study, an attempt was made to investigate the possibility of laser soldering using Sn-37Pb and Sn-3Ag-0.5Cu solderball. The laser energy absorbed on the pad raised the temperature of the solderball forming a reflowed solder bump. The result were discussed based on the measurement of pull and shear strength of the bond.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.80-86
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• 2009

This paper presents the plastic inhomogeneous deformation behavior of bimetal composite rods during the axisymmetric and steady-state extrusion process through a conical die. The rigid-plastic FE model considering frictional contact problem was used to analyze the co-extrusion process with material combinations of Cu/Al. Different cases of initial geometry shape for composite material were simulated under different conditions of co-extrusion process, which includes the interference and frictional conditions. From the simulation results, the sleeve cladding rate at the core/sleeve interface was recorded as a distribution of diameter ratio and interference conditions, which will be useful for the investigations of the bonding process during co-extrusion process. In addition, the results of the co-extrusion, connected with the results of the variations of diameter rate and average contact pressure, demonstrate a good agreement and present the possibility of describing the parameters of the plastic zones in non-uniform deformation of these type of composite materials.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.34-39
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• 2014

There are so many difficulties of melt bonding mainly applied for hull construction of a aluminum alloy small boat. For resolving this problem, Friction stir welding(FSW) in non-melting solid state welding Process generally is applied in the transport industry. This paper is studied the joining strength characteristics and macrostructure according to dissimilar aluminium 5000/6000 alloy joining for a small boat applied for this FSW technology. It is reported that difference of joining strength in accordance with the direction of rotation in case of friction stir welding between dissimilar metals(Al/Cu, Al/Fe) is also highly large. In this study, Test is carried out by making the specimen according to the direction of rotation of dissimilar aluminium alloy joining.

• Journal of Welding and Joining
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• v.29 no.5
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• pp.90-94
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• 2011

Ag metallic particles from nano-scale to submicron-scale are combined with organic solvent to provide fine circuits and interconnection. Ink-jet printing with Ag nano particle inks demonstrated the potentials of the new printed electronics technology. The bonding at the interface between the Ag wiring layer and the various substrates is very important. In this study, the details of interfaces in Ag wiring are investigated primarily by microstructure observation. By adjusting the materials and sintering conditions, nicely formed interfaces between Ag wiring and Cu, Au or organic substrates are achieved. In contrast, transmission electron microscope (TEM) image clearly shows interface debonding between Ag wiring and Sn substrate. Sn oxides are formed on the surface of the Sn plating. The formation of these is a root cause of the interface debonding.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.980-981
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• 2006

In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve full density of Carbon nanotube (CNT)/metal matrix composites with superior mechanical properties by improved particle bonding and least grain growth, which were considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (equal channel angular pressing), the most promising method in SPD, was used for the CNT/Cu powder consolidation. The powder ECAP processing with 1, 2, 4 and 8 route C passes was conducted at room temperature.

• Journal of the Korean institute of surface engineering
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• v.26 no.2
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• pp.71-81
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• 1993

Thed effects of Ar or Oxygen RF plasma treatment on the adhesion behavior of Cr films to polyimide sub-strates have been investigated by using SEM, XRD, AES, and $90^{\circ}$peel test. By applying RF plasma treatment of the polyimide surface prior to metal deposition, the peel adhesion strength of Cu/Cr films sputtered onto the fully cured BPDA-PDA polyimide was highly increased from about 3g/mm to 90 ~ 100g/mm. Improved peel adhesion strength of Cr/polyimide interfaces due to RF plasma treatment was attributed to the contributions from surface cleaning, Cr-polyimide bonding at the interface, and force required for plastic deformation of the film. While the surface topology change of the polyimide caused by RF plasma treatment makes a little contri-bution to the improved adhesion.

• ETRI Journal
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• v.35 no.2
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• pp.340-343
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• 2013

A novel bumping process using solder bump maker is developed for the maskless low-volume solder on pad (SoP) technology of fine-pitch flip chip bonding. The process includes two main steps: one is the aggregation of powdered solder on the metal pads on a substrate via an increase in temperature, and the other is the reflow of the deposited powder to form a low-volume SoP. Since the surface tension that exists when the solder is below its melting point is the major driving force of the solder deposit, only a small quantity of powdered solder adjacent to the pads can join the aggregation process to obtain a uniform, low-volume SoP array on the substrate, regardless of the pad configurations. Through this process, an SoP array on an organic substrate with a pitch of $130{\mu}m$ is successfully formed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.405-406
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• 2006

Raw materials from different sources, produced by a given process and having equal chemical composition, are supposed to be equivalent. The differences in sintering behavior have been investigated on P/M steels obtained from four diffusion-bonded powders (Fe + Ni + Cu + Mo) on atomized iron base, at the same alloy contents. Two levels of carbon and two sintering conditions have been investigated. Dimensional changes, C content, hardness, microhardness pattern, universal hardness, fractal analysis, pore features, microstructure features, and rupture strength have been compared to characterize different raw materials. The results show that the claimed equivalence is not confirmed by experimental data.

• Bulletin of the Korean Chemical Society
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• v.6 no.1
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• pp.7-11
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• 1985

The crystal structure of phlorizin, a ${\beta}$ -D-glucopyranoside of a flavonoid dihydrochalcone phloretin, has been determined by single crystal diffraction methods using diffractometer data obtained by the ${\omega}-2{\theta}$ scan technique with Cu $K{\alpha}$ radiation from a crystal with space group symmetry $P2_12_12_1$ and unit cell parameters a = 4.9094 (2), b = 19.109 (1), c = 23.275 (4) $\AA$. The structure was solved by direct methods and refined by full-matrix least-squares to a final R = 0.047 for the 1697 observed reflections. The dihydrochalcone moiety is flat and fully extended. The glucose ring has the $^4C_1$ chair conformation and the conformation of the primary alcohol group is gauche-gauche. The crystal packing is dominated by an extensive hydrogen bonding pattern. There are one strong and two weak intramolecular hydrogen bonds in the phlorizin molecule.

• Bulletin of the Korean Chemical Society
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• v.5 no.4
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• pp.158-162
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• 1984

The crystal structure of chloramphenicol base, $C_9H_{l2}N_2O_4$, the deacylated base of antibiotic chloramphenicol, has been determined by X-ray diffraction techniques using diffractometer data obtained by the ${\omega}-2{\theta}$ scan technique with CuK${\alpha}$ radiation from a crystal with space group symmetry $P2_12_12_1$ and unit cell parameters a = 22.322(6), b = 7.535(6), c = 5.781(5) ${\AA}$. The structure was solved by direct methods and refined by full-matrix least-squares to a final R = 0.051 for the 573 observed reflections. The overall conformation of the base is quite different from those of the chloramphenicol congeners which are similar despite the presence of many rotatable single bonds. The propane chain in the base is bent with respect to the phenyl ring, while it is extended in the chloramphenicol congeners. There is no intramolecular hydrogen bond between the hydroxyl groups of the propanediol moiety. All of the molecules in the crystal lattice are connected by a three-dimensional hydrogen bonding network.