Poling effects on the performance of a lead-free piezoelectric nanofiber in a structural health monitoring sensor

Ji, Sang Hyun,Cho, Jeong Ho,Paik, Jong-Hoo,Yun, Jondo,Yun, Ji Sun Elsevier 2017 Sensors and actuators. A, Physical Vol.263 No.-

<P><B>Abstract</B></P> <P>This study investigates the poling effects on the performance of a lead-free piezoelectric nanofiber module. The lead-free piezoelectric nanofiber of 0.78Bi<SUB>0.5</SUB>Na<SUB>0.5</SUB>TiO<SUB>3</SUB>-0.22SrTiO<SUB>3</SUB> (BNT-ST) and polyvinylidenefluoride (PVDF) is prepared by an electrospinning, and the lead-free piezoelectric nanofiber modules are fabricated with the bottom and top interdigitated electrodes. The poling effects on the performance of the lead-free piezoelectric nanofiber module were investigated by XRD and temperature-dependence dielectric properties. The possibility of a flexible structural health monitoring sensor application is confirmed by measuring the output voltage of the poled and unpoled lead-free piezoelectric nanofiber modules. The flexible lead-free piezoelectric nanofiber modules are directly attached on the structure with various shapes. We expect that this system will improve the efficiency of sensing. Tests on impact detection and the structural health monitoring based on the poled and unpoled lead-free piezoelectric nanofiber modules were carried out. The monitoring results confirm the potential for estimating impact location and problems with the structure, which have been observed more obviously in the poled lead-free piezoelectric nanofiber modules.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study investigates poling effects on the performance of a lead-free piezoelectric nanofiber module. </LI> <LI> The poling effects on the sensor characteristics of the lead-free piezoelectric nanofiber module were investigated by simulating several situations. </LI> <LI> The flexible lead-free piezoelectric nanofiber modules are directly attached on the structure with various shapes. </LI> <LI> The monitoring results confirm the potential for estimating impact location and problems with the structure. </LI> <LI> The poling process contributed greatly to the improvement of the sensing performance. </LI> </UL> </P>

CT실에서 무연보드 차폐체의 X선 차폐능력 평가

김성준,한태호,이효원,오유환,김승철,김정민 대한방사선과학회 2024 방사선기술과학 Vol.47 No.4

. This study compared the X-ray shielding abilities of the shields using Computed Radiography(CR) System after manufacturing a lead-free boards using gypsum and BaSO4, an eco-friendly X-ray shielding material. Total six lead-free boards were manufactured with BaSO4 concentrations of 25%, 50% and thickness of 10mm, 15mm, 20mm respectively, and additional thickness of 1.0 mm, 1.5 mm, 2.0 mm leads were prepared. In the experiment, Nine shields were placed on the Image Plate and placed in a Computed Tomography(CT) Room where CT scans were performed for 2 weeks. After that, the X-ray image of the shields were obtained through CR Reader, and Pixel Value(PV) were measured to evaluated the X-ray shielding abilities of the lead-free shields. The criterion for evaluating the shields was determined by comparing PV of lead-free board to that of the 1.5 mm thickness lead used in the CT rooms. As a result of the experiment, the PV of the lead-free boards within 25 % of the BaSO4 concentration and within 10 mm of the thickness were not enough to be used as X-ray shields in the CT Room because they did not reach the PV of the 1.5 mm thickness lead. BaSO4 concentration of 50 % at 20 mm thickness showed PV of 1.5 mm lead thickness or more indicating that it has an X-ray shielding ability to replace lead in the CT room

A Novel Cyclic Process Involving Zinc for Separating Silver from Lead-Free Solder Residue

Kim, Byung-Su,Lee, Jae-chun,Kim, Soo-Kyung The Japan Institute of Metals 2010 MATERIALS TRANSACTIONS Vol.51 No.7

<P>In recent years, the major issue posed by the recycling of tin-lead and lead-free solder residues is to recycle effectively lead-free solder residues because large volume of lead-free solder residues has been generated from electric and electronic industry as the environmental regulation becomes to be strictly in Europe. In general, the lead-free solder residues are generated from the step to affix components to printed circuit boards, which contains 2–4% of silver and 90–93% of tin. In this study, a novel cyclic process to separate silver from the lead-free solder residues using a metal solvent has been developed. The process uses zinc as a metal solvent which selectively forms intermetallic compounds with silver, followed by the volatilization separation step to recover zinc which can be reused as the metal solvent. Based on the results obtained, up to 90% of the silver in a lead-free solder residue was calculated to be separated into the dross phase through the sixth silver separation stage using the proposed process. This paper is only concerned with the results for the separation of silver from a lead-free solder residue using zinc as a metal solvent.</P>

무아레 간섭계를 이용한 유연 솔더와 무연 솔더 실장 WB-PBGA 패키지의 열-기계적 변형 거동

이봉희,김만기,주진원,Lee, Bong-Hee,Kim, Man-Ki,Joo, Jin-Won 한국마이크로전자및패키징학회 2010 마이크로전자 및 패키징학회지 Vol.17 No.3

반도체 패키지에 사용되고 있는 유연 솔더는 환경 보호 필요성 대문에 무연 솔더로 빠르게 대체되고 있다. 이와 같은 무연 솔더에 대한 여구는 주로 재료의 발견과 공정 적응성의 관점에서 이루어졌을 뿐, 기계적인 성질이나 신뢰성의 관점에서의 연구는 많이 이루어지지 않았다. 본 논문에서는 무아레 간섭계를 이용하여 유연 솔더와 무연 솔더 실장 WB-PBGA 패키지 결합체의 온도변화에 대한 열-기게적 거동을 해석하였다. 실시간 무아레 간섭계를 이용하여 각 온도 단계에서 변위 분포를 나타내는 간섭무늬를 얻고, 그로부터 유연과 무연의 솔더 조인트를 갖는 WB-PBGA 패키지의 굽힘 변형 거동 및 솔더 볼의 변형률을 비교 분석하였다. 분석결과를 보면 유연 솔더 실장 패키지 결합체의 솔더 볼은 칩경계 부근인 #3 솔더 볼에서 발생하는 전단변형률이 파손에 큰 영향을 미치며, 무연 솔더가 실장된 패키지 결합체의 솔더 볼은 가장 바깥 부근인 #7 솔더 볼에서 발행하는 수직 변형률이 파손에 큰 영향을 미칠 것으로 예측된다, 또한 무연 솔더 실장 패키지 결합체는 같은 온도 조건에서 유연 솔더 실장된 패키지에 비해 굽힘 변형이 휠씬 크게 발생될 뿐 아니라 솔더 볼의 유효변형률도 10% 정도 크게 발생하는 것으로 나타나서 열변형에 의한 파손에 취약할 것으로 예측된다. Pb-Sn solder is rapidly being replaced by lead-free solder for board-level interconnection in microelectronic package assemblies due to the environmental protection requirement. There is a general lack of mechanical reliability information available on the lead-free solder. In this study, thermo-mechanical behaviors of wire-bond plastic ball grid array (WB-PBGA) package assemblies are characterized by high-sensitivity moire interferometry. Experiments are conducted for two types of WB-PBGA packages that have Pb-Sn solder and lead-free solder as joint interconnections. Using real-time moire setup, fringe patterns are recorded and analyzed for several temperatures. Bending deformations of the assemblies and average strains of the solder balls are investigated and compared for the two type of WB-PBGA package assemblies. Results show that shear strain in #3 solder ball located near the chip shadow boundary is dominant for the failure of the package with Pb-Sn solder, while normal strain in #7 most outer solder ball is dominant for that with lead-free solder. It is also shown that the package with lead-free solder has much larger bending deformation and 10% larger maximum effective strain than the package with Pb-Sn solder at same temperature level.

유리단자용 무연(Pb-Free) 솔더 소재 및 공정 개발

정해원(Haewon Jeong),이선명(Sunmyoung Lee),박민호(Minho Park) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11

A new lead(Pb)-free solder material for automotive glass terminals is developed. In order to satisfy the regulation of EU ELV(End of Life Vehicle), the leaded solder in automotive glass should be replaced by lead-free solder. However, due to the unique property of the glass, it is easily broken with general electric lead-free solder material. As a result of the trying 120 types of solder material, we finally developed the excellent lead-free solder composition which has minimum Indium(In) contents. It is the optimized solder material against the wide range of thermal change environment. There is no glass crack with the developed lead-free solder. And it also shows good bonding strength enough to satisfy the automotive test standard.

자외선 LED를 이용한 자유 시안의 광촉매 산화

김성희(Seong Hee Kim),설정우(Woo Jeong Seol),이우춘(Woo Chun Lee),이상우(Sang Woo Lee),김순오(Soon Oh Kim) 大韓環境工學會 2015 대한환경공학회지 Vol.37 No.1

본 연구는 기존의 광촉매 산화 기술에서 주로 사용된 자외선램프의 단점을 보완할 수 있는 대체 광원인 자외선 LED를 사용하여 자유 시안을 폐수로부터 제거하는 공정을 평가하고자 수행되었다. 특히 광촉매 산화 공정의 다양한 영향 인자들에 대해 살펴보았다. 연구 결과, 자외선 LED는 기존의 광원인 자외선램프를 대체할 수 있는 적용성을 확인할 수 있었다. 뿐만아니라 LED 개수를 증가할수록 광촉매 산화 반응의 효율은 증가하였으나, 공정의 경제성과 효율성을 동시에 만족시키기 위해서는 최적의 LED의 개수를 선정할 필요가 있다는 것을 확인하였다. 광촉매로 이용된 아나타제(anatase), 루틸(rutile), Degussa P25 등 세 종류의 TiO₂ 중 Degussa P25가 가장 높은 성능을 보였으며, 아나타제(anatase)와 루틸(rutile)을 특별한 전처리 과정없이 단순하게 혼합하였을 때는 Degussa P25 만큼의 공정의 효율은 얻지 못했다. 또한 TiO₂의 입자 크기가 작을수록 광촉매산화 반응이 더욱 활발하게 이루어졌다. 그리고 광촉매 산화 반응에 있어 주로 전자 수용체 역할을 수행하는 산소를 주입함으로써 공정의 효율이 증진되는 효과를 얻을 수 있었다. This study was initiated to remove free cyanide from wastewater using the process of photocatalytic oxidation. UV lamp has been extensively used as a light source in conventional photocatalytic oxidation, but numerous drawbacks of UV lamp have been raised so far. Thus, this study focused on evaluating the applicability of UV LED as an alternative light source to overcome the drawbacks of UV lamp. Furthermore, the effects of diverse operational parameters on the performance of process were investigated. The results demonstrated the applicability of UV LED as a substitute of UV lamp. Also, the results show that the performance of process was improved by the increase in the number of UV LEDs used. To acquire economic feasibility as well as high efficacy, however, it is required to determine the optimum number of UV LED prior to practical implementation of the process. Among the three types of photocatalysts (anatase, rutile, and Degussa P25) tested, the Degussa P25 showed the greatest performance, and it was proven that the process was not improved as much as the Degussa P25 through simple mixing of anatase and rutile without any pretreatment. In addition, the removal efficiency of free cyanide appeared to be increased with the decrease in the particle size of TiO₂ photocatalyst. Besides, the process was enhanced with injection of oxygen which is considered as a major electron acceptor in the photocatalytic oxidation.

세라믹-금속 기반 LED 어레이 패키지의 저온동시소성시 휨발생 억제 연구

허유진,김효태,Heo, Yu Jin,Kim, Hyo Tae 한국마이크로전자및패키징학회 2016 마이크로전자 및 패키징학회지 Vol.23 No.4

고출력 LED 조명용 패키지를 제조함에 있어서 발열은 LED의 광출력과 수명에 매우 중요한 영향을 주는 인자로 알려져 있다. 본 연구에서는 가로등용 고출력 LED 패키지를 개발함에 있어서 효과적인 방열을 하기 위하여 방열효과가 상대적으로 우수한 구조인 chip-on-a-heat sink 구조를 가지는 세라믹-메탈 기반의 패키지를 제조하였다. 열확산 기능을 하는 heat sink 기판소재는 알루미늄 합금을, LED 어레이 회로를 형성하는 절연막으로는 저온동시소성용 glass-ceramics을 사용하였다. 특히 열처리 시 가장 이슈가 되는 세라믹-금속 하이브리드 패키지 기판의 휨을 억제하기 위한 수단으로서, glass-ceramic 절연막을 부분 코팅함으로써 휨현상을 용이하게 줄일 수 있게 되었다. 또한, LED 패키지의 방열특성의 향상 즉 열저항도 기존의 MCPCB 패키지나 전면 코팅형 절연막 패키지에 비해 훨씬 낮아지는 효과를 얻었을 뿐 아니라, 세라믹 코팅소재의 절감효과도 볼 수 있게 되었다. Ceramic-metal based high power LED array package was developed via thick film LTCC technology using a glass-ceramic insulation layer and a silver conductor patterns directly printed on the aluminum heat sink substrate. The thermal resistance measurement using thermal transient tester revealed that ceramic-metal base LED package exhibited a superior heat dissipation property to compare with the previously known packaging method such as FR-4 based MCPCB. A prototype LED package sub-module with 50 watts power rating was fabricated using a ceramic-metal base chip-on-a board technology with minimized camber deformation during heat treatment by using partially covered glass-ceramic insulation layer design onto the aluminum heat spread substrate. This modified circuit design resulted in a camber-free packaging substrate and an enhanced heat transfer property compared with conventional MCPCB package. In addition, the partially covered design provided a material cost reduction compared with the fully covered one.

픽셀 배치가 자유로운 임베디드 LED 전광판 모듈 및 제어장치 설계

이배규(Bae-Kyu Lee),김정화(Jung-Hwa Kim) 대한전자공학회 2013 전자공학회논문지 Vol.50 No.10

열 피로 하중을 받는 유/무연 솔더의 확률론적 신뢰성 평가

이억섭(Ouk Sub Lee),박연창(Yeon Chang Park),허만재(Man Jea Hur),김동혁(Dong Hyeok Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

The Soldering is known to be very effective technology for assembling of semiconductor. Recently, the concern for the lead-free solder is increasing, because of environmental problem and human body harmfulness of the lead solder. Therefore the property and efficiency of lead-free solder is actively studied by many researchers. In this study, the reliability estimation of the lead and lead-free solder is performed by using probability method and Thermal Fatigue Test. Using Tresca yield criterion, Life equation and FORM(first order reliability method), the results of the Thermal Fatigue Test are analyzed and the reliability of the lead and lead-free solder are systematically investigated.

Ring-Type Rotary Ultrasonic Motor Using Lead-free Ceramics

( Chang Hyo Hong ),( Hyoung Su Han ),( Jae Shin Lee ),( Ke Wang ),( Fang Zhou Yao ),( Jing Feng Li ),( Jung Ho Gwon ),( Nguyen Van Quyet ),( Jin Kyung Jung ),( Wook Jo ) 한국센서학회 2015 센서학회지 Vol.24 No.4

Ultrasonic motors provide high torques and quick responses compared to their magnetic counterparts; therefore, they are widely used in small-scale applications such as mobile phones, microrobots, and auto-focusing modules in digital cameras. To determine the feasibility of lead-free piezoceramics for ultrasonic motor applications, we fabricated a ring-type piezoceramic with a KNN-based lead-free piezoceramic (referred to as CZ5), intended for use in an auto-focusing module of a digital camera. The vibration of the lead-free stator was observed at 45.1 kHz. It is noteworthy that the fully assembled lead-free ultrasonic motor exhibited a revolution speed of 5-7 rpm, even though impedance matching with neighboring components was not considered. This result suggests that the tested KNN-based piezoceramic has great potential for use in ultrasonic motor applications, requiring minimal modifications to existing lead-based systems.