• Structural Engineering and Mechanics
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• 제73권6호
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• pp.667-684
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• 2020

In this article, the static responses of layered magneto-electro-thermo-elastic (METE) plates in thermal environment have been investigated through FE methods. By using Reddy's third order shear deformation theory (TSDT) in association with the Hamilton's principle, the direct and derived quantities of the coupled system have been obtained. The coupled governing equations of METE plates have been derived through condensation technique. Three layered METE plates composed of piezoelectric and piezomagnetic phases are considered for evaluation. For investigating the correctness and accuracy, the results in this article are validated with previous researches. In addition, a special attention has been paid to evaluate the influence of different electro-magnetic boundary conditions and pyrocoupling on the coupled response of METE plates. Finally, the influence of stacking sequences, magnitude of temperature load and aspect ratio on the coupled static response of METE plates are investigated in detail.

• Corrosion Science and Technology
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• 제14권3호
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• pp.113-119
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• 2015

Alloy 82/182 weld metals had been extensively used in joining the components of the PWR primary system. Unfortunately, there have been a number of incidents of cracking caused by PWSCC in Alloy 82/182 welds during the operation of PWR worldwide. To mitigate PWSCC, optimization of water-chemistry conditions, especially dissolved hydrogen (DH) and Zn contents, is considered as the most promising and effective remedial method. In this study, the PWSCC behaviours of Alloy 182 weld were investigated in simulated PWR environments with various DH content. Both in-situ and ex-situ oxide characterizations as well as PWSCC initiation tests were performed. The results showed that PWSCC crack initiation time was shortest in PWR water (DH: 30cc/kg). Also, high stress reduced crack initiation time. Oxide layer showed multi-layered structures consisted of the outer needle-like Ni-rich oxide layer, Fe-rich crystalline oxide, and inner Cr-rich inner oxide layers, which was not altered by the level of applied stress. To analyse the multi-layer structure of oxides, EIS measurement were fitted into an equivalent circuit model. Further analyses including TEM and EDS are underway to verify appropriateness of the equivalent circuit model.

• 한국레이저가공학회지
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• 제11권4호
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• pp.29-34
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• 2008

Ultraviolet laser micromachining has increasingly been applied to the electronics industry where precision machining of high-density, multi-layer, and multi material components is in a strong demand. Due to the ever-decreasing size of electronic products such as cellular phones, MP3 players, digital cameras, etc., flexible printed circuit board (FPCB), multi-layered with polymers and metals, tends to be thicker. In present, multi-layered FPCBs are being mechanically cut with a punching die. The mechanical cutting of FPCBs causes such defects as burr on layer edges, cracks in terminals, delamination and chipping of layers. In this study, the laser cutting mechanism of FPCB was examined to solve problems related to surface debris and short-circuiting that can be caused by the photo-thermal effect. The laser cutting of PI and FCCL, which are base materials of FPCB, was carried out using a pico-second laser(355nm, 532nm) and nano-second UV laser with adjusting variables such as the average/peak power, scanning speed, cycles, gas and materials. Points which special attention should be paid are that a fast scanning speed, low repetition rate and high peak power are required for precision machining.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.135-138
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• 2002

VCO(Voltage Controlled Oscillator) is one of the main components governing the size, performance and power consumption of telecommunication devices. As the devices become much smaller, VCO need to have much smaller size with better characteristics. Buried type passive components of L,C,R were developed previously and the structure of these components are good for minimizing the size of VCO. Our own library of passive components is used in simulation and fabrication of VCO circuit, and surface mounted components like varactor diode are analysed using the measurement circuit designed by ourselves. Two-Dimensional simulation of VCO circuit and local three-Dimensional structure simulation are performed and their relation is obtained. In structure of multi-layered VCO, some components governing the characteristics of VCO are selected and placed on the top of oscillator for the good tuning process. In resonator part, the stripline structure and low loss glass/ceramic material are used to get higher Q value. In our research, a VCO oscillates in the 2.3∼2.36 GHz band is developed.

• 한국항공우주학회지
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• 제48권5호
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• pp.383-390
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• 2020

다양한 산업분야에서 전자기판과 전장품의 기계적 체결을 위해 적용되는 웨지락(Wedge Lock)은 우주용 전장품에서도 장·탈착 용이성, 발사진동저감 효과 때문에 폭넓게 적용되고 있다. 그러나 기판의 가장자리에만 제한적으로 구속 가능한 장착 조건 때문에 기판의 크기가 증가할수록 극심한 발사환경에서의 굽힘거동에 의한 전자소자 솔더부의 피로수명 보장에 한계가 존재한다. 종래에는 상기 굽힘거동 최소화를 위해 기판에 별도의 보강재를 적용하였으나, 이는 전장품의 무게 및 부피증가가 불가피하다. 본 연구에서는 상기 한계점을 극복하고자, FR-4 재질의 박판을 기판의 배면부에 다층으로 적층하고, 각 층간에 점탄성 테이프를 적용하여 발사환경에서 소자의 피로수명 확보에 유리한 고댐핑 적층형 전자기판을 제안하였다. 본 적층형 기판의 설계 유효성 검증을 위해 상이한 온도조건에 따른 자유감쇠시험 및 인증 수준의 발사진동시험을 수행하였으며, 시험 결과에 기반한 고집적화 소자의 피로수명을 예측하였다.

• 마이크로전자및패키징학회지
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• 제25권4호
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• pp.59-66
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• 2018

본 논문에서는 수치해석을 사용하여 반도체용 패키지에 적용된 인쇄회로기판 (PCB(printed circuit board)) 구조를 다층 구조의 소재 특성을 모델링한 것과 단일 구조라고 가정한 모델링을 적용하여 warpage를 해석함으로써 단일 구조 PCB 모델링의 유용성을 분석하였다. 해석에는 3층과 4층 회로층을 갖는 PCB가 사용되었다. 또한 단일 구조 PCB의 재료 특성값을 얻기 위해 실제 제품을 대상으로 측정을 수행하였다. 해석 결과에 의하면 PCB를 다층 구조로 모델링한 경우에 비해 단일 구조로 모델링한 경우에 warpage가 증가하여 PCB 구조의 모델링에 따른 warpage 분석결과가 분명한 유의차가 있었다. 또한, PCB의 회로층이 증가하면 PCB의 기계적 특성인 탄성계수와 관성모멘트가 증가하여 패키지의 warpage가 감소하였다.

• 한국전자파학회논문지
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• 제24권4호
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• pp.357-365
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• 2013

기판 집적 도파관(Substrate Integrated Waveguide: SIW) 기술을 이용한 Ka 밴드의 35 GHz용 $4{\times}4$ 평면 배열 안테나를 제시한다. 전체 안테나 구조는 3층의 PCB(Printed Circuit Board) 적층 형태로 구성되며, top PCB에는 45도로 기울어진 직렬 방사 슬롯이 평면 배열로 방사부를 이룬다. 또한, 균일한 전력을 전달하고 안테나 전체 단면적을 최소화하기 위해 middle 및 bottom PCB에는 급전 SIW가 위치한다. 전체 안테나 개구면의 면적은 $750.76mm^2$이며, 유전율 2.2의 RT/Duroid 5880 기판을 적층하여 설계하였다. 각 방사부 및 급전부의 개별적인 전기적 특성은 full-wave 시뮬레이터인 CST MWS를 이용하여 확인하였다. 나아가 제안된 평면 배열 안테나는 대역폭 (490 MHz), 최대 이득(18.02 dBi), 부엽 레벨(-11.0 dB), 교차 편파 레벨(-20.16 dB)의 전기적 특성을 보인다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.319-319
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• 2013

Even though the fabrication methods of metal oxide based thin film capacitor have been well established such as RF sputtering, Sol-gel, metal organic chemical vapor deposition (MOCVD), ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD), an applicable capacitor of printed circuit board (PCB) has not realized yet by these methods. Barium Strontium Titanate (BST) and other high-k ceramic oxides are important materials used in integrated passive devices, multi-chip modules (MCM), high-density interconnect, and chip-scale packaging. Thin film multi-layer technology is strongly demanded for having high capacitance (120 nF/$mm^2$). In this study, we suggest novel multi-layer thin film capacitor design and fabrication technology utilized by plasma assisted deposition and photolithography processes. Ba0.6Sr0.4TiO3 (BST) was used for the dielectric material since it has high dielectric constant and low dielectric loss. 5-layered BST and Pt thin films with multi-layer sandwich structures were formed on Pt/Ti/$SiO_2$/Si substrate by RF-magnetron sputtering and DC-sputtering. Pt electrodes and BST layers were patterned to reveal internal electrodes by photolithography. SiO2 passivation layer was deposited by plasma-enhanced chemical vapor deposition (PE-CVD). The passivation layer plays an important role to prevent short connection between the electrodes. It was patterned to create holes for the connection between internal electrodes and external electrodes by reactive-ion etching (RIE). External contact pads were formed by Pt electrodes. The microstructure and dielectric characteristics of the capacitors were investigated by scanning electron microscopy (SEM) and impedance analyzer, respectively. In conclusion, the 0402 sized thin film multi-layer capacitors have been demonstrated, which have capacitance of 10 nF. They are expected to be used for decoupling purpose and have been fabricated with high yield.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1997년도 영남지회 학술발표회 논문집 Acoustic Society of Korean Youngnam Chapter Symposium Proceedings
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• pp.40-43
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• 1997

It is known tat the echoes from the most objects differ from the incident pulses in amplitude and frequency .Especially, the frequency in echoes from moving target is shiftby the Doppler effect. it causes to reduce the receiving sensitivity of piezoelectric transducers that have definite band width. The electric impedance, whichis connected to the electrical terminals, notably changes the resonant frequency of a thickeness mode piezoelectric vibrator with high electromechanical doupling due to the electroelastic effect. Using this effect, we have developed a frequency controllable ultrasonic transducer which is mad eof multi-layered PZT disks to adjust to frequency shifted by Doppler effect. The characteristics of transducer can be obtained by using the equivalent circuit of transmission line model. It was confirmed experimentally that the center frequency and band width of the trasducer could be controlled by the conditions of the electrical terminals. These results coincided with theoretical results.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.156-159
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• 2002

Film Bulk Acoustic wave Resonator (FBAR) using thin piezoelectric films can be fabricated as monolithic integrated devices with compatibility to semiconductor process, leading to small size, low cost and high Q RF circuit elements with wide applications in communications area. This paper presents a MMIC compatible Suspended FBAR using surface micromachining. It is possible to make Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$membrane by using surface micromachining and its good effect is to remove the substrate silicon loss. FBAR was made on 2$\mu\textrm{m}$ multi-layered membrane using CVD process. According to our result, Fabricated film bulk acoustic wave resonator has two adventages. First, in the respect of device Process, our Process of the resonator using surface micromachining is very simple better than that of resonator using bull micromachining. Second, because of using the multiple layer, thermal expansion coefficient is compensated, so, the stress of thin film is reduced.