• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1541-1550
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• 2001

This paper describes experimental investigations in the direct extrusion of copper clad aluminum rods through conical dies. Composite materials consist of two or more different material layers. Copper clad aluminum composite materials are being used fur economic and structural purposes and the development of an efficient production method of copper clad aluminum composite material rods by extrusion is very important, It is necessary to know the conditions in which successful uniform extrusion ,and sound cladding may be carried out without any defects in the direct extrusion. There are several variables that have an influence on determining a sound clad extrusion. In order to investigate the influence of these parameters on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with various extrusion temperatures, extrusion ratios and semi-cone angles of die. Subsequently, the microscopic inspection of interface bonding is carried out for extruded products. By measuring hardness, along extrusion way of products, a variation of hardness has been discussed. Proportional flow state has been considered by measuring radius ratio of Cu sleeve and Al core before and after extrusion.

• Journal of Welding and Joining
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• v.29 no.4
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• pp.93-99
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• 2011

This study was performed to compare the shear strength of the bondings between stainless steel crown/direct type composite resin and stainless steel crown/indirect type composite resin. Four groups of bonding conditions were prepared. Two groups of bonding conditions were made by the indirect type composite resin system and the other two groups were made by the direct type composite resin system. The shear strength tests were carried out using universal testing machine, Model 4465 of Instron Co.. It was indicated that the bond strength values of the indirect type composite resins were higher than those of the direct type composite resins. TE-SE group was superior to the TE-ONE in indirect type resin system. These results were thought to be the high degree of the polymerization accompanied with temperature and pressure of the resin of indirect type resin. It was also found that indirect composite resin contains less amount of porosity in resin.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.139-139
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• 2012

With angle resolved photoemission spectroscopy (ARPES), the surface electronic band structures of Pt3Co (111) and Pt3Ni (111) single crystals are investigated, which allow to study the bonding interaction between chemically absorbed atomic oxygen and its surfaces. The d-band electrons of subsurface TM are separated from the direct chemical bonding with atomic oxygen. That is, the TM does not contribute to direct chemical bonding with oxygen. From the density functional theory (DFT) calculations, it is identified that the main origin of improved oxygen absorption property, i.e. softening of Pt-O bonding, is due to the suppression of Pt surface-states which is generated from change of interlayer potential, i.e. charge polarization, between Pt-top and TM-subsurface. Our results point out the critical roles of subsurface TM in modifying surface electronic structures, which in turn can be utilized to tune surface chemical properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.874-877
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• 2001

SOI(Silicon-On-Insulator) technology is proposed as an alternative to bulk silicon for MEMS(Micro Electro Mechanical System) manufacturing. In this paper, we fabricated the SOI wafer with uniform active layer thickness by silicon direct bonding and mechanical polishing processes. Specially-designed electrostatic bonding system is introduced which is available for vacuum packaging and silicon-glass wafer bonding for SOG(Silicon On Glass) wafer. We demonstrated thermopile sensor and RF resonator using the SOI wafer, which has the merits of simple process and uniform membrane fabrication.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.437-440
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• 2000

Composite material consists of more than two materials and make various kinds of composite materials by combining different single materials. Copper clad aluminum composite material is composed of Al and Cu, and it has already been put to practical use in Europe because of its economic benefits. This paper presents the interface bonding according to the variation of extrusion ratio and semi-angle die by observing the interface between Cu and Al using metal microscope. By that result, we can predict the conditions of the interface bonding according to the extruding conditions.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.799-805
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• 2015

The further development of information, communication and digital media technologies requires the use of advanced, miniaturized semiconductor chips that operate at a high frequency. Die bonding and wire bonding methods for semiconductor packaging have been replaced by direct attachment to the substrate after forming a bump on the chip. However, the height of the bump or ball is an important factor for defects during assembly. This paper proposes an algorithm to measure the height of the bumps or balls in semiconductor packaging with greater accuracy. The performance of the proposed algorithm is experimentally validated. Non-contact 3D measurements of a shiny round ball is quite difficult, and it is not easy to obtain accurate data. This paper thus proposes an optical method and technique to improve the measurement accuracy.

• ETRI Journal
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• v.37 no.5
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• pp.951-960
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• 2015

For a conventional power metal-oxide-semiconductor field-effect transistor (MOSFET), there is a trade-off between specific on-state resistance and breakdown voltage. To overcome this trade-off, a super-junction trench MOSFET (TMOSFET) structure is suggested; within this structure, the ability to sense the temperature distribution of the TMOSFET is very important since heat is generated in the junction area, thus affecting its reliability. Generally, there are two types of temperature-sensing structures-diode and resistive. In this paper, a diode-type temperature-sensing structure for a TMOSFET is designed for a brushless direct current motor with on-resistance of $96m{\Omega}{\cdot}mm^2$. The temperature distribution for an ultra-low on-resistance power MOSFET has been analyzed for various bonding schemes. The multi-bonding and stripe bonding cases show a maximum temperature that is lower than that for the single-bonding case. It is shown that the metal resistance at the source area is non-negligible and should therefore be considered depending on the application for current driving capability.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.23-33
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• 2021

Two main technologies of III-V/Si laser diode for optical communication, direct epitaxial growth, and wafer bonding were studied. Until now, the wafer bonding has been vigorously studied and seems promising for the ideal III-V/Si laser. However, the wafer bonding process is still complicated and has a limit of mass production. The development of a concise and innovative integration method for silicon photonics is urgent. In the future, the demand for high-speed data processing and energy saving, as well as ultra-high density integration, will increase. Therefore, the study for the hetero-junction, which is that the III-V compound semiconductor is directly grown on Si semiconductor can overcome the current limitations and may be the goal for the ideal III-V/Si laser diode.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.499-502
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• 2005

A process map has been developed, which can identify the process conditions for weak mechanical bonding at the contact surface during the direct extrusion of a Cu-Ti bimetal bar. Bonding mechanism between Cu and Ti was assumed as a cold pressure welding. Then, the plastic deformation at the contact zone causes mechanical bonding and a new bonding criterion for pressure welding was developed as a function of the principal stretch ratio and normal pressure at the contact surface by analyzing micro local extrusion at the contact zone. Finite element analyses for extrusion of Cu-Ti bimetal bars were performed for various process conditions. The deformation history at the contact surface was traced and the proposed new bonding criterion was applied to predict whether the mechanical bonding at the Cu-Ti contact surface happens. Finally, a process map for the extrusion of Cu-Ti bimetal bar is suggested.

• Korean Journal of Materials Research
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• v.12 no.6
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• pp.508-512
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• 2002

$2000{\AA}-SiO_2/Si(100)$ and $560{\AA}-Si_3N_4/Si(100)$ wafers, which are 10 cm in diameter, were directly bonded using a rapid thermal annealing method. We fixed the anneal time of 30 second and varied the anneal temperatures from 600 to $1200^{\circ}C$. The bond strength of bonded wafer pairs at given anneal temperature were evaluated by a razor blade crack opening method and a four-point bonding method, respectively. The results clearly slow that the four-point bending method is more suitable for evaluating the small bond strength of 80~430 mJ/$\m^2$ compared to the razor blade crack opening method, which shows no anneal temperature dependence in small bond strength.