• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.95-95
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• 2009

Lead-free $(K_{0.5}Na_{0.5})(Nb_{0.96}Sb_{0.04)O_3$ + 1.2 mol% $K_4CuNb_8O_{23}$ + x mol% $Fe_2O_3$ ceramics were manufactured by a conventional solid state reaction method. And then, their piezoelectric and dielectric properties were investigated. At the 0.2 mol% $Fe_2O_3$ doped ceramics, the values of Kp=0.436 and Qm=696.36 were obtained, respectively, which were suitable for piezoelectric transformer application.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.15-23
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• 2015

Lead-free bonding has attracted significant attention for automotive power device packaging due to the upcoming environmental regulations. Silver (Ag) is one of the prime candidates for alternative of high Pb soldering owing to its superior electrical and thermal conductivity, low temperature sinterability, and high melting temperature after bonding. In this paper, the bonding technology by Ag paste was introduced. We classified into two Ag paste bonding according to applied pressure, and each bonding described in detail including recent studies.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.11
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• pp.991-996
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• 2011

This study was carried out vibration attenuation of vibration absorber attached to the cantilever beam structure. Modern tank guns are stabilized to allow fire on the move while traversing uneven terrain. However, as the length of the barrel is extended, to meet required muzzle exit velocities, the terrain induced vibrations lead to increased muzzle pointing errors. Thus, reducing these vibrations should lead to increased accuracy. The vibration absorber includes a compliant energy storage device, such as a spring, and a mass secured to the energy storage device. In this study, it accomplished a research in about gun barrel vibration attenuation using tuned mass damper. The barrel was hung from a bungee cord for free-free condition. It accomplished a vibration experiment for verified attenuation efficiency.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1255-1257
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• 2005

The increase of secondary electron-emitting coefficient is effective to reduce the discharge voltage as well as to improve the luminance efficiency of PDP. We investigated the properties of ${\gamma}$ with composition and different dielectric constants, and the microstructure of dielectric after ion collision. As a result the dielectric of PbO system showed higher ${\gamma}$ compared with Pb-free system. However, there was no difference in ${\gamma}$ when the MgO protective layer was covered.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.302-302
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• 2010

The lead-free piezoelectric ceramics must have high piezoelectric properties and electrical properties for the applications of piezoelectric devices. Therefore, KNN ceramics were investigated as a function of the variation of Nb. The density was increased with the increase of Nb. The density was saturated above 0.8895 mol Nb. The maximum value of electromechanical coupling coefficient(kp) was obtained 0.428 at 0.8895mol Nb. This result can be attributed to the well sintered of specimens. Also, The maximum value of mechanical quality factor(Qm) showed 1554 at 0.8895mol Nb. Therefore, this composition can be used for application of piezoelectric device such as piezoelectric transformer and piezoelectric actuator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.305-305
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• 2010

In this study, in order to develop excellent lead free piezoelectric ceramics for piezoelectric transformer application (Na,K)(Nb,Sb)$O_3$ ceramics were fabricated using conventional oxides mixed method and their piezoelectric and dielectric characteristics were investigated according to the amount of $Bi_2O_3$ addition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.335-335
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• 2010

$SiO_2$, $B_2O_3$, $Al_2O_3$, CaO, MgO, $Na_2O$, $ZrO_2$, $Bi_2O_3$를 이용하여 성질이 다른 두 종류의 무연계 프릿트를 제조하여 특성을 표준화 하였고, 이들 무연계 프릿트를 이용하여 Ag계 도체 및 $RuO_2$계 저항페이스트롤 제조하여 특성에 미치는 프릿트 조성의 영향을 연구하였다. $B_2O_3$를 첨가하여 퍼짐특성이 큰 프릿트의 경우 더 우수한 페이스트 특성을 나타내었다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.137-143
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• 2008

Thermal fatigue life prediction for solder joints becomes the most critical issue in present microelectronic packaging industry. And lead-free solder is quickly becoming a reality in electronic manufacturing fields. This trend requires life prediction models for new solder alloy systems. This paper describes the life prediction models for SnAgCu and SnPb solder joints, based upon non-linear finite element analysis (FEA). In case of analyses of the SnAgCu solder joints, two kinds of shapes are used. As a result, it is found that the SnAgCu solder has longer fatigue life than the SnPb solder in temperature cycling analyses.

• Advances in materials Research
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• v.2 no.3
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• pp.173-180
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• 2013

Lead-free complex perovskite ceramics $NaMeO_3$ ($Me{\equiv}Nb$, Ta) were synthesized using conventional solid state reaction technique and characterized by structural, FTIR and electrical (dielectric and ac conductivity) studies. The crystal symmetry, space group and unit cell dimensions were determined from the experimental results using FullProf software. XRD analysis of the compound indicated the formation of single-phase orthorhombic structure with the space group Pmmm (47). Dielectric studies showed the diffuse phase transition at $394^{\circ}C$ for $NaNbO_3$ and $430^{\circ}C$ for $NaTaO_3$. Ac conductivity in both the compounds follows Jonscher's power law.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.157-162
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• 2010

This paper describes the thermal fatigue life prediction models for 95.5Sn-4.0Ag-0.5Cu solder joints of Flip chip package considering Under Bump Metallurgy(UBM). A 3D Finite element slice model was used to simulate the viscoplastic behavior of the solder. For two types of solder bump pitches, simulations were analyzed and the effects of underfill packages were studied. Consequently, it was found out that solder joints with underfill had much better fatigue life than solder joints without underfill, and solder joints with $300{\mu}m$ bump pitch had a longer thermal fatigue life than solder joints with $150{\mu}m$ bump pitch. Through the simulations, flip chip with lead-free solder joints should be designed with underfill and a longer bump pitch.