• Korean Journal of Metals and Materials
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• v.47 no.3
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• pp.202-208
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• 2009

The effects of aging time on the microstructure and shear strength of the Low Temperature Co-fired Ceramic (LTCC)/Ag pad/Electroless Nickel Immersion Gold (ENIG)/BGA solder joints were investigated through isothermal aging at $150^{\circ}C$ for 1000 h with conventional Sn-37Pb and Sn-3Ag-0.5Cu. $Ni_3Sn_4$ intermetallic compound (IMC) layers was formed at the interface between Sn-37Pb solder and LTCC substrate as-reflowed state, while $(Ni,Cu)_3Sn_4$ IMC layer was formed between Sn-3Ag-0.5Cu solder and LTCC substrate. Additional $(Cu,Ni)_6Sn_5$ layer was found at the interface between the $(Ni,Cu)_3Sn_4$ layer and Sn-3Ag-0.5Cu solder after aging at $150^{\circ}C$ for 500 h. Thickness of the IMC layers increased and coarsened with increasing aging time. Shear strength of both solder joints increased with increasing aging time. Failure mode of BGA solder joints with LTCC substrate after shear testing revealed that shear strength of the joints depended on the adhesion between Ag metallization and LTCC. Fracture mechanism of Sn-37Pb solder joint was a mixture of ductile and pad lift, while that of Sn-3Ag-0.5Cu solder joint was a mixture of ductile and brittle $(Ni,Cu)_3Sn_4$ IMC fracture morphology. Failure mechanisms of LTCC/Ag pad/ENIG/BGA solder joints were also interpreted by finite element analyses.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.611-615
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• 2003

The crystalline and dielectric properties on $Al_2O_3$ filled glass frit ($CaO-Al_2O_3-SiO_2-MgO-B_2O_3$) with admixtures of $TiO_2$ have been investigated. The dielectric constant value of $7.5{\sim}7.8$, quality factor value of 700 were obtained for glass frit : $Al_2O_3$ (50 : 50 wt%) ceramics. As the amount of $TiO_2$ increased, temperature coefficient of dielectric constant were decreased.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.11
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• pp.680-686
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• 2004

An integrated inductor using the low temperature cofiring ceramics(LTCC) technology was fabricated. The inductor has Ag circular spiral coil with 16 turns (2-turn x 8-layer) and has a dimension of 11.52mm diameter and 0.71mm thick. For the fabricated inductor, calculation method of inductance was given and it is confirmed that the calculated value is very close to the measured one. Finally as an application of the LTCC integrated inductor to low power electronic circuits, a LTCC buck DC/DC converter with 1.32W output power and 1MHz switching frequency using the inductor fabricated was developed. For the converter the maximum efficiency of about 81% was obtained.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.362-370
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• 2010

In this paper, a compact RF Front-end module for Wireless Fidelity(Wi-Fi) and Worldwide Interoperability for Microwave Access(WiMAX) applications is realized by low temperature co-fired ceramic(LTCC) technology. The RF Front-end module is composed of three LTCC band-pass filters, a Film Bulk Acoustic Resonator(FBAR) filter, fully embedded matching circuits, an SPDT switch for mode selection, an SPDT switch for Tx/Rx selection, and an SP4T switch for band selection. The parasitic elements of 0.2~0.3 pF are generated by the structure of stacking in the top pad pattern for DC block capacitor of SPDT switch for mode selection. These kinds of parasitic elements break the matching characteristic, and thus, the overall electrical performance of the module is degraded. In order to compensate it, we insert a parallel lumped-element inductor on capacitor pad pattern for DC block, so that we obtain the optimized performance of the RF Front-end module. The fabricated RF front-end module has 12 layers including three inner grounds and it occupies less than $6.0mm{\times}6.0mm{\times}0.728mm$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1106-1111
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• 2006

To improve warpage, delamination and the chemical reaction between 2 different co-fired materials, the bonding behavior with common glass was studied. As shown in the previous paper, the phenomenon of the infiltration is different with the composition of the glass. In particular, in the case of low temperature melting glass, infiltration is experimented in this study. GA-1 glass is infiltrated among $BaTiO_3$ particles below $800^{\circ}C$ and is made by glass/ceramic composite. Until the laminate is fired under $850^{\circ}C$, provskite phase is observed. Although in the case of GA-12 glass, the temperature of the glass infiltration is lower than it of GA-l glass, the perovskite phase already disappears at $800^{\circ}C$. As a result, GA-1 and GA-12 glasses are infiltrated among particles at low temperature, however, the chemical reactivity of the glass/ceramic and sintering temperature should be considered.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.121-125
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• 2002

이동통신기기 등의 고주파용 LTCC(Low Temperature Co-fired Ceramic) LC filter의 소결결에 있어 기존의 소결공정인 전기로 소결공정과 microwave를 이용한 소결공정을 이용하여 소결하였을때 LC filter의 수축율과 무게감소, 그에 따른 밀도의 변화, SEM을 이용한 표면형상 분석을 통해 급속가열을 통한 공정시간의 단축, 낮은 에너지 소비로 인한 제조단가의 절감, 균일한 가열로 인한 소결온도의 저하 등의 장점을 갖는 microwave sintering을 적용할 수 있는 가능성을 제시하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.958-966
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• 2012

This paper presents a compact bluetooth/WiFi dual-mode dual-band RF front-end module(FEM) is realized by low temperature co-fired ceramic(LTCC) technology. The proposed RF front-end module consists of a diplexer, baluns in the LTCC substrate, and an SPDT switch, an SP3T switch on the LTCC substrate. In order to reduce the module size and increase integration level, the proposed diplexer and balun are designed using LC lumped elements. The parasitic elements caused by coupling effect between metal pattern layers and ground plane layer are considered during the design. The fabricated dual-mode RF front-end module has 13 pattern layers including three inner ground layers and it occupies less than $3.0mm{\times}3.7mm{\times}0.66mm$.

• Journal of the Korean Ceramic Society
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• v.44 no.5 s.300
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• pp.173-178
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• 2007

The microstructure and microwave dielectric properties of dolomite type borates, $CaZr(BO_3)_2$ ceramics prepared by conventional mixed oxide method were explored. The sintering temperature of $CaZr(BO_3)_2$ ceramics could be reduced from $1150^{\circ}C\;to\;925^{\circ}C$ with little amount of sintering additives. Microwave dielectric properties of 3 wt% $Bi_2O_3-CuO$ added $CaZr(BO_3)_2$ ceramics sintered at $925^{\circ}C$ were $K{\approx}10.4,\;Q{\times}f{\approx}80,000GHz\;and\;TCF{\approx}+2ppm/^{\circ}C$. Thus obtained LTCC tape was co-fired with Ag paste for compatibility test and revealed no sign of Ag reaction with the ceramics. Therefore, $CaZr(BO_3)_2$ ceramics is considered as a possible candidate material for low temperature co-fired multilayer devices.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.37-41
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• 2004

As mobile communication devices use wide bands for large data transmission, Low Temperature Co-fired Ceramic(LTCC) has been a candidate for module substrate, for it provides better electrical properties and enables various embedded passive devices compared to conventional PCB. The LTCC, however, has applied in limited area because of non-uniform shrinkage. Hybrid heating was developed to raise sample temperature uniformly in a short period of time This leads to unidirectional sintering which enables sample to be sintered layer by layer from the bottom, resulting in more stable shape of interconnection at the top surface of the sample than conventional electric furnace heating. When sintering properties of substrate and electrical/mechanical properties of interconnection were compared, hybrid heating showed possibility to be applicable to substrate miniaturization and interconnection densification superior to electric furnace heating.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.154-161
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• 2011

This paper presents a compact integrated transceiver module for 2.4 GHz band applications using Low Temperature Co-fired Ceramic(LTCC) technology. The implemented transceiver module is divided into an RF Front-End Module (FEM) part and a transceiver IC chip part. The RF FEM part except an SPDT switch and DC block capacitors is fully embedded in the LTCC substrate. The fabricated RF FEM has 8 pattern layers and it occupies less than $3.3\;mm{\times}5.2\;mm{\times}0.4\;mm$. The measured results of the implemented RF FEM are in good agreement with the simulated results. The transceiver IC chip part consists of signal line, power line and transceiver IC for 2.4 GHz band communication system. The fabricated transceiver module has 9 layers including three inner grounds and it occupies less than $12\;mm{\times}8.0\;mm{\times}1.1\;mm$. The implemented transceiver module provides an output power of 18.1 dBm and a sensitivity of -85 dBm.