• Proceedings of the KWS Conference
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• 2003.05a
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• pp.193-195
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• 2003

Micro-structure and shear properties with reflow conditions, reflow temperature and time, for In-48Sn solder on BGA package were examined at the temperature between 140 and 170$^{\circ}C$ for 10 to 3600sec. With increasing reflow temperature and time, the thickness of intermetallic compound formed between solder and pad increased. Shear test indicated shear force increased in the range to a critical value of reflow time, and decreased over a critical reflow time. With increasing reflow temperature and time, the crater occurred on fracture surface because of a increase of crater by voids and IMC particles precipitated in solder.

• Proceedings of the KSR Conference
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• 2002.10b
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• pp.820-825
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• 2002

As the speed of rail transit is higher, it is very important to secure the safety and confidence of the braking device and in the point of view, by means of the rise of the temperature from the friction between the disk and pad which are the actual part of a braking system, the damage of brake disk is the main cause to lose the safety of braking device. Therefore, in this study, to predict the danger of a disk brake and to know its max. temperature in the train service the module of a temperature measurement by the non-contact method was developed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.555-556
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• 2007

Through the single head kinematics, sliding distance is a movement of a pad within wafer. The sliding distance is very important to frictional heat, material removal, and so on. A Temperature distribution is similar to sliding distance. But is not same. Because of complex process factor in CMP. A platen velocity is a dominant factor in a temperature and material removal. WIWNU is low in head faster condition.

• Journal of the Korean Society of Clothing and Textiles
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• v.41 no.5
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• pp.872-882
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• 2017

There are no specific guidelines on how to control the heat input for the heat generating smart base layer. This study investigated the mode of actuating heat pad attached to the base layer by performing a human wear test in a cold environment. Subjects participating in the test wore T-shirts, jumper and pants on the base layer with heating pads. Skin temperature, total time of heating and the number of switching for the heating mode were observed as the subject controlled the heating mode voluntarily. The comfortable range of skin temperature on the abdomen was larger than on the lower back. The subject felt hot and turned off the switch when the mean skin temperature of the abdomen was $48.8^{\circ}C$ and the lower back was $40.1^{\circ}C$. The total heating time and the number of actuating switching were larger for women than men. The voluntary action of heating for men with high cold sensitivity was significantly different from men with low cold sensitivity. Therefore, it is necessary (depending on gender and cold sensitivity) to set the heating mode differently for the automatic heat control of a future smart base layer.

• Analytical Science and Technology
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• v.25 no.3
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• pp.164-170
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• 2012

Cyanoacrylate fuming mehod is effective for latent fingerprints developing on non-porous surfaces. In this study, we investigated optimal conditions for latent fingerprint development using cyanoacrylate fuming method in vacuum chamber. The effects of temperature, relative humidity, fuming method and processing time were checked throughly. The amount of evaporated cyanoacrylate was increased at higher temperature, but cyanoacrylate polymerization on the fingerprint ridge was best at $30^{\circ}C$. With a relative humidity of 40% to 50% conditions, good quality of fingerprints were developed. If a relative humidity is lower than 30% or higher than 60%, polymerization rate of cyanoacrylate monomers on the fingerprint ridge was decreased. It was identified that application of $OMEGA-PRINT^{TM}$ dispersal pad or cotton ball with sodium hydroxide fuming method in vacuum chamber was more effective than natural fuming method. We found that cyanoacrylate processing time in vacuum chamber did not have more significant than relative humidity.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.54-56
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• 2005

Ultrasonic soldering using of Si-wafer to FR-4 PCB atroom temperature was investigated. Sn3.5Ag foil rolled $100{\mu}m$ was used for solder. The UBM of Si-die was Cu/ Ni/ Al from top to bottom and its thickness was $0.4{\mu}m$, $0.4{\mu}m$, $0.3{\mu}m$ respectively. Pad on FR-4 PCB comprised of Au/ Ni/ Cu from top to bottom and its thickness was $0.05{\mu}m$, $5{\mu}m$, $18{\mu}m$ respectively. The ultrasonic soldering time was changed from 0.5sec to 3.0sec and its power 1400W. As experimental result, reliable bond joint by ultrasonic at room temperature was obtained. The shear strength increased with soldering time up to 2.5 sec. That means at 2.5sec, the shear strength showed maximum rate of 65.23N. The strength decreased to 33.90N at 3.0 sec because the cracks generated along the intermetallic compound between Si-wafer and Sn-3.5mass%Ag solder. intermetallic compound produced by ultrasonic between the solder and the Si-die was $(Cu, Ni)_{6}Sn_{5}$ and the intermetallic compound between solder and pad on FR-4 was $(Ni, Cu)_{3}Sn_{4}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.6-12
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• 2019

Bonding properties of epoxy-containing solder joints were investigated by a high temperature aging test. Specimens were prepared by bonding an R3216 standard chip resistor to an OSP-finished PCB by a reflow process with two basic types of solder (SAC305 & Sn58Bi) pastes and two epoxy-solder (SAC305+epoxy & Sn58Bi+epoxy) pastes. In all epoxy solder joints, an epoxy fillet was formed in the hardened epoxy, lying around the outer edge of the solder joint, between the chip and the Cu pad. In order to analyze the bonding characteristics of solder joints at high temperatures, a high-temperature aging test at $150^{\circ}C$ was carried out for 14 days (336 h). After aging, the intermetallic compound $Cu_6Sn_5$ was found to have formed in the solder joint on the Cu pad, and the shear stress on the conventional solder joint was reduced by a significant amount. The reason that the shear force did not decrease much, even though in epoxy solder, was thatbecause epoxy hardened at the outer edge of the supported solder joints. Using epoxy solder, strong bonding behavior can be ensured due to this resistance to shear force, even in metallurgical changes such as those where intermetallic compounds form at solder joints.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.204-209
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• 2016

The analyses on self-heating effect in 7 nm node non-rectangular Bulk FinFET device were performed using 3D device simulation with consideration to contact via and pad. From self-heating effect simulation, the position where the maximum lattice temperature occurs in Bulk FinFET device was investigated. Through the comparison of thermal resistance at each node, main heat transfer path in Bulk FinFET device can be determined. Self-heating effect with device parameter and operation temperature was also analyzed and compared. In addition, the impact of interconnects which are connected between the device on self-heating effect was investigated.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.93-100
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• 2003

This paper describes the thermoelastic instability arising from friction heat generation in braking and proposes the finite element methods to predict the variation of temperature and thermal deformation. In a conventional disc brake analysis, heat generation is only related with wheel speed and friction material and the interface pressure between disc and pad is assumed constant. But under dynamic braking conditions, the frictional heat causes the thermoelastic distortion that leads to more concentrated contact pressure distribution and hence more and more non-uniform temperature. In this paper, to complete the solution of the thermomechanically coupled problem, the linear relation model between pressure and temperature is proposed and demonstrated in examples of a simple two dimensional contact problem. And the two dimensional model has been extended to an annular three dimensional disc model in order to consider more realistic geometry and to provide a more accurate critical speed for automotive brake systems.

• Tribology and Lubricants
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• v.19 no.5
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• pp.268-273
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• 2003

This paper presents hot spot behaviors on the rubbing surface of disk-pad type brake by using coupled thermal-mechanical analysis technique. The height of micro-asperity on the rubbing surface is usually 2∼3 ${\mu}$m in practical disk brakes. Non-uniform micro-contacts between the disk and the rigid friction pads lead to high local temperature distributions, which may cause the material degradation, and develop hot spots, thermal cracks, and brake system failure at the end for a braking period. The friction temperatures on the rubbing surface of disk brakes in which are strongly related to the hot spot and thermal related wears are rapidly concentrated on the micro-contact asperities during braking. The computed FEM results show that the contact stress, friction induced temperature and thermal strain are highly concentrated on the rubbing micro-contact asperities even though the braking speed and force are small during the braking period. This hot spot may directly produce the slippage and various thermal wears on the brake-rubbing surface.