• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.253-255
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• 2002

Since a butt Joint is smaller than a lap type joint, it is expected to have smaller AC losses. The butt joint is produced by the diffusion bonding of the contacting surface under pressured and heated condition. It is important to find robust joining conditions, because butt joint has small contact area and has the shape by which the quality of bonding is hard to be checked. In this research, the loading pressure is considered as the joining parameter to find optimum joining condition. The DC resistance of the joint may be changed by the surface pressure during joining process, because the superconducting strands near the contact surface are failed by large plastic deformation. The range from 10 MPa to 18 MPa is expected optimum surface pressure in the conditions of 1 hour heating time and $750^{\circ}C$ temperature in the vacuum furnace.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.10
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• pp.883-888
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• 2002

SiC direct bonding technology is very attractive for both SiCOI(SiC-on-insulator) electric devices and SiC-MEMS(micro electro mechanical system) fields because of its application possibility in harsh environments. This paper presents pre-bonding techniques with variation of HF pre-treatment conditions for SiC wafer direct bonding using PECVD(plasma enhanced chemical vapor deposition) oxide. The PECYD oxide was characterized by XPS(X-ray photoelectron spectrometer) and AFM(atomic force microscopy). The characteristics of the bonded sample were measured under different bonding conditions of HF concentration and an applied pressure. The bonding strength was evaluated by the tensile strength method. The bonded interface was analyzed by using SEM(scanning electron microscope). Components existed in the interlayer were analyzed by using FT-IR(fourier transform infrared spectroscopy). The bonding strength was varied with HF pre-treatment conditions before the pre-bonding in the range of 5.3 kgf/cm$^2$to 15.5 kgf/cm$^2$.

• International Journal of Advanced Culture Technology
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• v.8 no.2
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• pp.246-251
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• 2020

Dimethyl Ether(DME) engine use a highly efficient alternative fuel having a great quantity of oxygen and has a advantage no polluting PM gas. The existing DME fuel cam material is a highly expensive carbide alloy, and it is difficult to take a price advantage. Therefore the study of replacing body area with inexpensive steel material excluding piston shoe and contact area which demands high characteristics is needed. The development of WC-Ni base carbide alloy optimal bonding composition technique was accomplished in this study. To check out the influence of bonding temperature and time, bonding characteristics of sintering temperature was experimented. The hardness of specimen and bonding rate were measured using ultrasound equipment. The bonding state of each condition was excellent, and the thickness of mid-layer, temperature and maintaining time were measured. The mid-layer thickness according to bonding temperature and maintaining time were observed with optical microscope. We analyzed the micro-structural analysis, formation of bonding specimen, wafer fabrication and fuel cam abrasion test. Throughout this study, we confirmed that the fuel cam for DME engine which demands high durability against velocity and pressure is excellent.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.1
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• pp.53-59
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• 2009

The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the micro channel heat exchangers using diffusion bonding technology. Four types of heat exchangers are designed and manufactured, which are straight type, long dot type, splited wavy type and straight double side type. Heat transfer and pressure drop performance of each heat exchangers are measured in various operating conditions, and compared each other. The results show that the $(j/f)^{1/3}$ performance of splited wavy type and long dot type increases about 10.3% and 6.1% at the Reynolds number 470 compared to that of straight type, respectively. On the other hand, $(j/f)^{1/3}$ performance of straight double side type decreases 19.7%.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2304-2309
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• 2008

The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the micro channel heat exchangers using diffusion bonding technology. Four types of heat exchangers are designed and manufactured, which are straight type, long dot type, splited wavy type and straight double side type. Heat transfer and pressure drop performance of each heat exchangers are measured in various operating conditions, and compared each other. The results show that the $(j/f)^{1/3}$ performance of splited wavy type and long dot type increases about 10.3% and 6.1% at the Reynolds number 470 compared to that of straight type, respectively. On the other hand, $(j/f)^{1/3}$ performance of straight double side type decreases 19.7%.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.254-255
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• 2002

Optical elements such as small glass lenses or optical fibers can be permanently bonded to substrates using Al inter-layer by applying Pressure and heating. As an example aspherical lens was bonded on a silicon V-groove. The bonding has high shear strength and good thermal cycling stability.

• Transactions of Materials Processing
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• v.5 no.1
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• pp.37-46
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• 1996

Superplastic forming/diffusion bonding (SPF/DB) processes were analyzed using a rigid visco-plastic finite element method. The optimum pressure-time relationship for a target strain rate and thickness distributions were predicted by two-node line elements based on the membrane approximation for plane strain. Material behavior during SPF/DB of the integral structures having complicated shapes was investigated. The tying condition is employed for the analysis of inter-sheet contact problems. A movement of rib structure is successfully predicted during the forming.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.90-98
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• 1997

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of friction pressure on bonding strength and a charicteristic of fracture. The tensile strength of the friction welded joint was increased up to 90% of the Cu base metal under the condition of friction time 1.2 sec, friction pressure 4.5kgf/$\textrm{mm}^2$ and upset pressure 10kgf/$\textrm{mm}^2$. From the results of fracture surface analysis, the increase of friction pressure could remarkably decrease the force and the time to be normally acted on weld interface. The W particles which were included in the plastic zone of Cu side could induce fracture adjacent to the weld interface because their existance in Cu induces a decrease in available section area and an increase in notch effect. Therefore, the tensile strength was decreased at high friction pressure (6kgf/$\textrm{mm}^2$) because the destruction of W was increased by an increase in mechanical force and crack was formed at weld interface.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.1
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• pp.12-19
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• 2015

As a measure of improving the mechanical properties of a diffusion bonded joint of a ferritic/martensitic steel (FMS), the post-bonding heat treatment (PBHT) is applied. In the temperature range of normalizing condition ($950-1,050^{\circ}C$), diffusion bonding is employed with compressive stress (6 MPa). Due to the martensite structure distributed in the matrix, Vicker's hardness values of the as-bonded are much higher than those of the as-received. Through the PBHT for 1 h at $720^{\circ}C$, hardness values are recovered to as low as those of the as-received condition. Also, tensile properties of PBHT are similar to those of the as-received at up to the test temperature of $550^{\circ}C$, when the diffusion bonding is carried out over $1,000^{\circ}C$. Based on the creep-rupture testing performed at $650^{\circ}C$ in air environment, the joint efficiency of the PBHTed specimens is about 80% in, which is higher than that of the as-bonded specimens.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.199-204
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• 2009

The effect of temperature on ACF thermocompression bonding for FPD assembly was investigated, It was found that Au bumps on driver IC's were not bonded to the glass substrate when the bonding temperature was below $140^{\circ}C$ so bonds were made at temperatures of $163^{\circ}C$, $178^{\circ}C$ and $199^{\circ}C$ for further testing. The bonding time and pressure were constant to 3 sec and 3.038 MPa. To test bond reliability, FPD assemblies were subjected to thermal shock storage tests ($-30^{\circ}C$, $1\;Hr\;{\leftrightarrow}80^{\circ}C$, 1 Hr, 10 Cycles) and func! tionality was verified by driver testing. It was found all of FPDs were functional after the thermal cycling. Additionally, Au bumps were bonded using ACF's with higher conductive particle densities at bonding temperatures above $163^{\circ}C$. From the experimental results, when the bonding temperature was increased from $163^{\circ}C$ to $199^{\circ}C$, the curing time could be reduced and more conductive particles were retained at the bonding interface between the Au bump and glass substrate.