• Journal of Sensor Science and Technology
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• v.22 no.1
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• pp.89-94
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• 2013

In this paper, we developed a beam of MEMS probe card using a BeCu sheet. Silicon wafer thickness of $400{\mu}m$ was fabricated by using deep reactive ion etching (RIE) process. After forming through silicon via (TSV), the silicon wafer was bonded with BeCu sheet by soldering process. We made BeCu beam stress-free owing to removing internal stress by using joule heating. BeCu beam was fused by using joule heating caused by high current. The fabricated BeCu beam measured length of 1.75 mm and width of 0.44 mm, and thickness of $15{\mu}m$. We measured fusing current as a function of the cutting planes. Maximum current was 5.98 A at cutting plane of $150{\mu}m^2$. The proposed low-cost and simple fabrication process is applicable for producing MEMS probe beam.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1061-1066
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• 2006

This paper presents the electrical characteristics with manufacturing process and performance evaluation of high performance zinc oxide varistors. ZnO varistors were fabricated with typical ceramic production methods with different thickness and the structural and electrical characteristics of ZnO varistors were investigated. All varistors exhibited high density, which was in the range of $5.41{\sim}5.49g/cm^3$. In the electrical properties, the reference voltage increased in the range of $4.410{\sim}5.250kV$ with increasing their thickness and the residual voltage exhibited the same trends as the reference voltage. In the long duration current impulse withstand test, E-2 and F-1 samples failed at the two and four shots of impulse current, respectively, but E-1 and F-2 samples survived 18 shots during the test. Before and after this test, the variation ratio of residual voltage of E-1 and F-2 samples were -0.34 % and 0.05 %, respectively, which were in the acceptance range of 5 %. According to the results of tests, it is thought that if the fabrication process such as insulating coating, sintering condition, and soldering method is improved, these ZnO varistors would be possible to apply to the station class arresters in the near future.

• Journal of the Korean Solar Energy Society
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• v.35 no.1
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• pp.29-34
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• 2015

The photovoltaic ribbon attached the flux reduces the solar module manufacturing process and the pollution. This paper presents an analytical method for solving the continuous flux drying system of photovoltaic ribbon. Also, some experiments of the drying of photovoltaic ribbon are carried out in order to design the drying system. Numerical results indicate the air temperature, the air velocity, the air pressure and the timewise temperature variation of ribbon during drying process. In case of the drier process length is short, 400mm, the photovoltaic ribbon is wet. Thus, another study of drying system is necessary to improve the drying ability. As a result, multi-stage drier system is proposed and shown to be good drying ability.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.07a
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• pp.119-126
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• 2001

Chip-on-glass(COG) mounting of area array electronic packages was attempted by heating the rear surface of a contact pad film deposited on a glass substrate. The pads consisted of an adhesion(i.e. Cr or Ti) and a top coating layer(i.e. Ni or Cu) was heated by an UV laser beam transmitted through the glass substrate. The laser energy absorbed on the pad raised the temperature of a solder ball which is in physical contact with the pad, forming a reflowed solder bump. The effects of the adhesion and top coating layer on the laser reflow soldering were studied by measuring temperature profile of the ball during the laser heating process. The results were discussed based on the measurement of reflectivity of the adhesion layer. In addition, the microstructures of solder bumps and their mechanical properties were examined.

• Journal of Welding and Joining
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• v.25 no.2
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• pp.76-81
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• 2007

Solder bumps have been used to interconnect the chip and substrate, and the size of the solder bump decreases below $100{\mu}m$ to accommodate higher packaging density. In order to fabricate solder bumps, a mold to chip transfer process is suggested in this work. Since the thin stainless steel mold is not wet by the solder, the molten solder is forced to fill the mold cavities with ultrasonic vibration. The solders within the mold cavities are transferred to the Cu pads on the polyimide film through reflow soldering.

• Applied Microscopy
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• v.45 no.2
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• pp.89-94
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• 2015

This article briefly reviews the results of recently reported research on high-temperature Pb-free solder alloys and the research trend for characterization of the interfacial reaction layer. To improve the product reliability of high-temperature Pb-free solder alloys, thorough research is necessary not only to enhance the alloy properties but also to characterize and understand the interfacial reaction occurring during and after the bonding process. Transmission electron microscopy analysis is expected to play an important role in the development of high-temperature solders by providing accurate and reliable data with a high spatial resolution and facilitating understanding of the interfacial reaction at the solder joint.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.51-59
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• 1998

The purposes of the paper are to consider the failure phenomenon based on delamination and crack when the encapsulant of plastic IC package under hygrothermal loading in the IR soldering process is on elastic and viscoelastic behavior due to the temperature and to show the optimum design using fracture mechanics. The model for analysis is the plastic SOJ package with a dimpled diepad. The package model with the perfect delamination between chip and diepad is chosen to estimate the resistance to fracture by calculating J-integrals in low temperature and C(t)-integrals in high temperature with the change of the design under hygrothermal loading. The optimum design to depress the delamination and crack in the plastic IC package is presented.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.230-232
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• 2006

Eutectic Au-20Sn solder has been widely used for optoelectronic packages because of fluxless soldering process and thus are particularly valuable for many applications such as biomedical, photonic, and MEMS devices that can not use any flux. Also when good joint strength, superior resistance to corrosion, whisker-free, and good thermal conductivity are demanded, eutectic Au-20Sn solder can be satisfied with above-mentions best. In this study, we tried to know the interfacial reactions between Au-20Sn solder and Cu substrate with or without ENIG plating layer In the results, Au-Cu-Sn ternary phases were formed at the Au-20Sn/Cu substrate, and Au-Ni-Sn, Au-Ni-Cu-Sn phases were formed at the Au-20Sn/ENIG substrate.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.59-63
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• 2010

Immersion Sn plating was produced on Cu foil by distributing nano-sized diamonds (ND). The ND distributed on the coating surface broke the continuity of Sn-oxide layer, therefore leading to penetrate the molten solder through the oxide and retarding the wettability degradation during a reflow process. Furthermore, the ND in the Sn coating played a role of diffusion barrier for Sn atoms and decreased the growth rate of intermetallic compound ($Cu_6Sn_5$) layer during the solid-state aging. The study confirmed the importance of ND to improve the wettability and reliability of the Sn plating. Complete dispersion of the ND within the immersion Sn plating needs to be further developed for the electronic packaging applications.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.3
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• pp.296-303
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• 2004

Recently, the ultra light metal structure with periodic and three dimensional truss elements takes attention because of its multi-functionality and substantial heat resistance. However, the complicated fabrication process leading to high cost has been a major obstacle to wide applications. In this paper, a new idea to construct an ultra light structure with periodic, three dimensional truss using metal wires is presented. To prove the practical validity, a Kagome-like structure was fabricated from stamped wires and punched face sheets. It was assembled by soldering. Through three-point bending and compression tests, the strength was evaluated and compared with the theory.