• Journal of the Microelectronics and Packaging Society
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• v.20 no.4
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• pp.25-30
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• 2013

Pb-free ferroelectric $(Na_{0.5}Bi_{0.5})TiO_3$ (NBT) thin films were prepared by a modified sol-gel process. Their structural, dielectric and pyroelectric properties were investigated as a function of the excess Na/Bi ratio and the annealing temperature. In the case of thin films containing no excess Na and Bi, only partial amounts of the perovskite NBT were crystallized, where the films consisted mainly of the pyrochlore phase of $Bi_2Ti_2O_7$ for annealing conditions of $600{\sim}800^{\circ}C$. With increasing excess Na/Bi ratio, the proportion of the perovskite phase effectively increased due to the compensation of the volatile Na and Bi components. For a Na/Bi ratio of 2.0, the thin film with single NBT perovskite phase was obtained within XRD detection limit after annealing at $700^{\circ}C$ for 10 min and it showed the excellent dielectric properties, ${\varepsilon}r$ of ~550 and tan ${\delta}$ of 0.03. While these properties were degraded for Na/Bi ratio of 2.5 despite the existence of pure perovskite phase. The NBT thin film with Na/Bi ratio of 2.0 are also promising candidates for applications requiring pyroelectric devices because it was found to have pyroelectric coefficients of $1.3{\sim}7nC/cm^2K$ in the temperature range of $30{\sim}100^{\circ}C$.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.221-225
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• 2003

The MFIS-FET(Field Effect Transistor) devices using $BLT/Y_2O_3$ buffer layer on p-Si(100) substrates were fabricated by the Sol-Gel method and conventional memory processes. The crystal structure, morphologies and electrical properties of prepared devices were investigated by using various measuring techniques. From the C-V(capacitance-voltage) data at 5V, the memory window voltage of the $Pt/BLT/Y_2O_3/si$ structure decreased from 1.4V to 0.6V with increasing the annealing temperature from $700^{\circ}C\;to\;750^{\circ}C$. The drain current (Ic) as a function of gate voltages $(V_G)$ for the $MFIS(Pt/BLT/Y_2O_3/Si(100))-FET$ devices at gate voltages $(V_G)$ of 3V, 4V and 5V, the memory window voltages increased from 0.3V to 0.8V as $V_G$ increased from 3V to 5V.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.49-53
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• 2011

Diamond-like carbon (DLC) films is a metastable form of amorphous carbon containing a significant fraction of Sp3 bond. DLC films have been characterized by a range of attractive mechanical, chemical, tribological, as well as optical and electrical properties. In this study DLC films were prepared by the RF magnetron sputter system on $SiO_2$ substrates using graphite target. The effects of the post annealing temperature on the Property variation of the DLC films were examined. The DLC films were annealed at temperatures ranging from 300 to $500^{\circ}C$ using rapid thermal process equipment in vacuum. The variation of electrical property and surface morphology as a function of annealing treatment was investigated by using a Hall Effect measurement and atomic force microscopy. Raman and X-ray photoelectron spectroscopy analyses revealed a structural change in the DLC films.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.27-32
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• 2010

For the flip chip joints processed using Cu pillar bumps and Sn pads, thermal cycling and high temperature storage reliabilities were examined as a function of the Sn pad height. With increasing the height of the Sn pad, which composed of the flip chip joint, from 5 ${\mu}m$ to 30 ${\mu}m$, the contact resistance of the flip chip joint decreased from 31.7 $m{\Omega}$ to 13.8 $m{\Omega}$. Even after thermal cycles of 1000 times ranging from $-45^{\circ}C$ to $125^{\circ}C$, the Cu pillar flip chip joints exhibited the contact resistance increment below 12% and the shear failure forces similar to those before the thermal cycling test. The contact resistance increment of the Cu pillar flip chip joints was maintained below 20% after 1000 hours storage at $125^{\circ}C$.

• Journal of Preventive Medicine and Public Health
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• v.28 no.1 s.49
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• pp.1-12
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• 1995

Diatomaceous earth, quarried from the remains of aquatic plants deposited millions of years ago, continues to be a very important raw material with many industrial uses. In its natural state, diatomaceous earth is an amorphous silica with no crystalline pattern. For many uses, however, it is calcinated and calcination converts a portion of the amorphous silica to a crystalline form, cristobalite which is far more fibrogenic. In a factory which produces calcinated diatomaceous earth, seven workers were proved as pneumoconiosis on 1991 and 1992. Authors reviewed medical chart and current status of them. Authors also examined thirty one subjects from the factory with questionnaire, physical examination, spirometry and chest radiography on August 13th 1993. The radiographs were independently interpreted by two radiologists and their findings were classified by International Classification of Radiography of Pneumoconiosis(ILO, 1980). Total and respirable dust of diatomaceous earth were measured on October 1993. The results were as follows; 1. Of 31 workers, 6 (19.4%) were diagnosed as diatomaceous earth pneumoconiosis. There was an increasing tendency in prevalence of pneumoconiosis as the duration of dust exposure gets longer. 2. There were no significant differences in age, smoking rate, alcohol drinking rate, and pulmonary function test results between cases and non-cases. 3. The means of total dust exposures at flour manufacturing, fire brick grinding and packaging, ceramic raws packaging processes exceeded Korean and ACGIH standards, $10mg/m^3$. Above results suggest that engineering controls, periodic environmental and medical surveillance are important for preventing pneumoconiosis in the diatomite factory.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.2
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• pp.23-30
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• 1999

The relationships between morphological structures and residual stress behaviors of polyimide thin films depending on isomeric diamines were investigated. For this study, Poly(phenylene biphenyltetracarboximide) (BPDA-PDA) and poly(oxydiphenylene biphenyltetracarboximide) (BPDA-ODA) films were prepared from their isomeric diamines: 1,3-phenylene diamine (1,3-PDA) 1,4-phenylene diamine (1.4-PDA), 3,4'-oxydiphenylene diamine (3,4'-ODA), and 4,4'-oxydiphenylene diamine (4,4'-ODA), respectively. For those films, residual stresses were detected in-situ during thermal imidization of the isomeric polyimide as a function of processing temperature over the range of 25~$400^{\circ}C$ using. Thin Film Stress Analyzer (TFSA). In comparison, residual stress of BPDA-1.4PDA having better in-plain orientation and chain order was the lowest value of 7MPa whereas those of BPDA-1,3-PDA, BPDA-3,4'-ODA, and BPDA-4,4'-ODA were in the range of 40-50MPa. Conclusively, the effect of morphological nature (chain rigidity, chain order, orientation) and chain mobility relating to the g1ass transition behavior on the residual stress of isomeric polyimide thin films wart analyzed.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.1
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• pp.7-11
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• 2009

In this study, solder joints were made with Sn-3.5Ag (wt%) solder ball. Electroless nickel / immersion gold (ENIG) printed circuit board (PCB) substrates were employed in this work. The mechanical and electrical properties were measured as a function of the number of reflow. Die shear strength was measured with increasing reflow number. Until the forth or fifth reflow, shear force increased and after the fifth reflow the shear force of die decreased. The electrical resistivity of solder joint linearly increased with increasing reflow number.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.25-31
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• 2010

In this study, we investigated the morphology and thermal stability of interfacial phases in joint between lead free solder(Sn-3.0Ag-0.5Cu) and electroless Ni-W-P under bump metallizations(UBM) with different tungsten contents as a function of thermal aging. Content of phosphorus of each deposits was fixed at 8 wt.%, and content of tungsten was variated each 0, 3, 6 and 9 wt.%. Specimens were prepared by reflowing at $255^{\circ}C$, aging range was $200^{\circ}C$ and up to 2 weeks. After reflow process, in the electroless Ni(W)-P/solder joint, the interfacial intermetallic compound(IMC) was showed both $(Cu,Ni)_6Sn_5$ and $(Ni,Cu)_3Sn_4$. UBM and generated IMC at the interface of lead free solder was proportionally increased with aging time. The thickness of IMC was increased because the generation rate of $Ni(W)_3P$ decreased with increasing contents of W.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.121-128
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• 2005

Solder joints in microelectronic devices are frequently operated at an elevated temperature in service. They also experience plastic deformation caused by temperature excursion and difference in thermal expansion coefficients. Deformed solders can go through a recovery and recrystallization process at an elevated temperature, which would alter their microstructure and mechanical properties. In this study, to predict the changes in mechanical properties of Pb-free solder joints at high temperatures, the high temperature microhardness of several Pb-free and composite solders was measured as a function of temperature, deformation, and annealing condition. Solder alleys investigated include pure Sn, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, Sn-2.8Ag-7.0Cu (composite), and Sn-2.7Ag-4.9Cu-2.9Ni (composite). Numbers are all in wt.$\%$ unless specified otherwise. Solder pellets were cast at two cooling rates (0.4 and $7^{\circ}C$/s). The pellets were compressively deformed by $30\%$ and $50\%$ and annealed at $150^{\circ}C$ for 2 days. The microhardness was measured as a function of indentation temperature from 25 to $130^{\circ}C$. Their microstructure was also evaluated to correlate with the changes in microhardness.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.49-53
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• 2007

The direct methanol fuel cell (DMFC) is a promising power source for portable applications due to many advantages such as simple construction, compact design, high energy density, and relatively high energy-conversion efficiency. In this work, an electrochemical methanol sensor for monitoring the methanol concentration in direct methanol fuel cells was fabricated using a thin composite nafion membrane as the electrolyte. We have analyzed the I-V characteristic of the fabricated methanol sensor as a function of methanol concentration, catalyst electrode and platinum(Pt) thickness. The fabricated sensor was analyzed by I-V measurement with various methanol concentration. When we measured the sensor characteristics with 10nm Pt and at 1V, the current value was $1.30{\times}10^{-6}A,\;1.96{\times}10^{-6}A\;and\;2.80{\times}10^{-6} A$ for three methanol concentration of 1M, 2M and 3M, respectively. When the methanol concentration was fixed at 2M, the current value of the fabricated device with Pt layers of 5, 10 and 15 nm thickness was $3.06{\times}10^{-6}A,\;1.96{\times}10^{-6}A\;and\;1.00{\times}10^{-6}A$, respectively. These results lead us to the conclusion that when the methanol concentration increases, the output current increases and when the catalyst electrode become thinner, the current increase more. It showed that, the thinner the catalyst electrode, the more electrochemistry become activation.