• 한국생산제조학회지
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• 제20권5호
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• pp.559-563
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• 2011

Drop impact reliability assessment of solder joints on the flip chip is one of the critical issues for micro system packaging. Our previous researches have been showing that new solder ball compositions of Sn-3.0Ag-0.5Cu has better mechanical reliability than Sn-1.0Ag-0.5Cu. In this paper, dynamic reliability analysis using Finite Element Analysis (FEA) is carried out to assess the factors affecting flip chip in drop simulation. The design parameters are size and thickness of chip, and size, pitch and array of solder ball with composition of Sn1.0Ag0.5Cu. The board systems by JEDEC standard including 15 chips, solder balls and PCB are modeled with various design parameter combinations, and through these simulations, maximum yield stress and strain at each chip are shown at the solder balls. It is found that larger chip size, smaller chip array, smaller ball diameter, larger pitch, and larger chip thickness have bad effect on maximum yield stress and strain at solder ball of each chip.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1673-1678
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• 2007

The use of flip-chip type electronic package offers numerous advantages such as reduced thickness, improved environmental compatibility, and downed cost. Despite numerous benefits, flip-chip type packages bare several reliability problems. The most critical issue among them is their electrical performance deterioration upon consecutive thermal cycles attributed to gradual delamination growth through chip and adhesive film interface induced by CTE mismatch driven shear and peel stresses. The electronic package in use is heated continuously by itself. When the crack at a weak site of the electronic package occurs, thermal deformationon the chip side is changed. Therefore, we can measure these micro deformations by using Moire interferometry and find out the crack length.

• 한국초전도ㆍ저온공학회논문지
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• 제7권1호
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• pp.17-20
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• 2005

We has designed, fabricated, and measured a Single flux quantum (SFQ) toggle flip-flop (TFF). The TFF is widely used in superconductive digital electronics circuits. Many digital devices, such as frequency counter, counting ADC and program counter be used TFF Specially, a program counter may be constructed based on TFF We have designed the newly TFF and obtained high bias margins on test. In this work, we used two circuit simulation tools, WRspice and Julia, as circuit optimization tools. We used XIC for a layout tool. Newly designed TFF had minimum bias margins of +/- $37\%$ and maximum bias margins of +/-$37\%$(enhanced from +/- $37\%$). The designed circuits were fabricated by using Nb technology The test results showed that the re-optimized TFF operated correctly on 100kHz and had a very wide bias margins of +/- $53\%$.

• Archives of Plastic Surgery
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• 제46권2호
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• pp.176-180
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• 2019

Post-traumatic soft tissue defects sometimes require sequential flap coverage to achieve complete healing. In the era of propeller flaps, which were developed to reduce donor site morbidity, Feng et al. introduced the concept of the free-style puzzle flap, in which a previously harvested flap becomes its own donor site by recycling the perforator. However, when a perforator cannot be found with a Doppler device, we suggest performing a new type of flap, the flip-flap puzzle flap, which combines two concepts: the free-style puzzle flap and the flip-flap flap described by Voche et al. in the 1990s. We present the cases of three patients who achieved complete healing through this procedure.

• 한국엔터테인먼트산업학회논문지
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• 제13권4호
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• pp.241-253
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• 2019

이 연구는 대학생들에게 플립러닝 수업을 진행함에 있어 최소한의 처치를 하였을 때 일어나는 현상들을 알아보고, 학생들이 학습에 대한 즐거움을 느낄 수 있도록 개선을 위하여 좋았던 점과 아쉬운 점을 제시하고자 하였다. 따라서 최근에 새롭게 대두되는 플립러닝 수업기법을 대학수업에 적용하는데 필요한 기초자료를 제공과 장단점을 알아보는 데 목적을 둔다. 이 연구의 방법은 플립러닝에 대한 인식을 알아보기 위하여 설문지조사를 실시하였다. 이 연구결과를 토대로 다음과 같은 결론을 제시하고자 한다. 첫째, 플립러닝 수업 경험은 대학생들이 처음 접하는 비율이 50%로 나타났다. 둘째, 학생들은 교수자가 의도한 플립러닝 수업의 실천(동영상 시청)에서 매우 낮은 경향을 보였다. 셋째, 대학생들은 교과목의 사전학습 준비에 소홀한 학습습관을 지니고 있다. 넷째, 동영상 제공을 통한 플립러닝 수업에 대한 인식은 높은 긍정으로 나타났다. 다섯째, 플립러닝 수업은 기본적으로 가지고 있는 시간과 장소에 구애받지 않고 학습할 수 있는 장점이 있으나 실질적으로 시험이나 성적에 반영되지 않으면, 학생들의 적극적 참여는 낮다는 점이다. 결론적으로, 대학생들은 초등학생 시기부터 다양한 학습기법의 적용으로 인해 인센티브 방식의 수업에 익숙하여 자발적 학습참여를 어렵게 한다는 점을 알 수 있었다.

• 한국치위생학회지
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• 제20권2호
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• pp.155-166
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• 2020

Objectives: The purpose of this study is to prove, through the design and operation of a teaching learning model for clinical dental hygiene and practice III, the effectiveness of the flipped learning PARTNER model. Methods: A professional council was formed, composed of three professors of dental hygiene and one professor of education; each member was an expert with a Ph.D. From December 2018 to February 2019. Results: Learning preferences for the clinical learning hygiene curriculum based on flip learning showed that it had higher accessibility than traditional teaching methods. Subjects' motivation to learn was improved through flip learning, their critical thinking ability was improved through active discussion and flip team discussion, and their self-directed learning ability was also improved. Participation increased through flipped learning, and subjects' skill abilities showed their highest score by improving their performance through the whole lecture. A high satisfaction of 4.54 out of 5 points was achieved. Conclusions: It was confirmed that the development and operation of a flipped learning-based clinical hygiene curriculum can provide an effective and satisfactory learning process.

• Biomolecules & Therapeutics
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• 제23권1호
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• pp.31-38
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• 2015

Histone acetylation plays a critical role in the regulation of transcription by altering the structure of chromatin, and it may influence the resistance of some tumor cells to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) by regulating the gene expression of components of the TRAIL signaling pathway. In this study, we investigated the effects and molecular mechanisms of trichostatin A (TSA), a histone deacetylase inhibitor, in sensitizing TRAIL-induced apoptosis in Caki human renal carcinoma cells. Our results indicate that nontoxic concentrations of TSA substantially enhance TRAIL-induced apoptosis compared with treatment with either agent alone. Cotreatment with TSA and TRAIL effectively induced cleavage of Bid and loss of mitochondrial membrane potential (MMP), which was associated with the activation of caspases (-3, -8, and -9) and degradation of poly (ADP-ribose) polymerase (PARP), contributing toward the sensitization to TRAIL. Combined treatment with TSA and TRAIL significantly reduced the levels of the cellular Fas-associated death domain (FADD)-like interleukin-$1{\beta}$-converting enzyme (FLICE) inhibitory protein (c-FLIP), whereas those of death receptor (DR) 4, DR5, and FADD remained unchanged. The synergistic effect of TAS and TRAIL was perfectly attenuated in c-$FLIP_L$-overexpressing Caki cells. Taken together, the present study demonstrates that down-regulation of c-FLIP contributes to TSA-facilitated TRAIL-induced apoptosis, amplifying the death receptor, as well as mitochondria-mediated apoptotic signaling pathways.

• 마이크로전자및패키징학회지
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• 제19권3호
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• pp.49-56
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• 2012

최근 전자 제품의 소형화, 박형화 및 집적화에 따라 칩과 기판을 연결하는 범프의 미세화가 요구되고 있다. 그러나 범프의 미세화는 직경 감소와 UBM의 단면적 감소로 인하여 전류 밀도를 증가시켜 전기적 단락을 야기할 수 있다. 특히 범프에서 형성되는 금속간화합물과 KV의 형성은 전기적 및 기계적 특성에 큰 영향을 줄 수 있다. 따라서 본 논문에서는 유한요소해석을 이용하여 플립칩 범프의 열변형을 분석하였다. 우선 TCT의 온도조건을 통하여 플립칩 패키지의 열변형 특성을 분석한 결과, 범프의 열 변형이 시스템의 구동에 큰 영향을 미칠 수 있음을 확인하였다. 그리고 범프의 열변형 특성에 큰 영향을 미칠 것을 생각되는 IMC층의 두께와 범프의 직경을 변수로 선정하여 온도변화, 열응력 및 열변형에 대한 해석을 수행하였으며, 이를 통하여 IMC층이 범프에 영향을 미치는 원인에 대한 분석을 수행하였다.

• Journal of Welding and Joining
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• 제33권5호
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• pp.41-46
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• 2015

The snap cure NCP(non-conducive paste) adhesive material is essentially required for the high productivity flip chip bonding process. In this study, the accessibility of DEA(dielectric analysis) method for the evaluation of snap cure behavior was investigated with comparison to the isothermal DSC(differential scanning calorimetry) method. NCP adhesive was mainly formulated with epoxy resin and imidazole curing agent. Even though there were some noise in the dielectric loss factor curve measured by DEA, the cure start and completion points could be specified clearly through the data processing of cumulation and deviation method. Degree of cure by DEA method which was measured from the variation of the dielectric loss factor of adhesive material was corresponded to about 80% of the degree of cure by DSC method which was measured from the heat of curing reaction. Because the adhesive joint cured to the degree of 80% in the view point of chemical reaction reveals the sufficient mechanical strength, DEA method is expected to be used effectively in the estimation of the high speed curing behavior of snap cure type NCP adhesive material for flip chip bonding.

• 한국해안·해양공학회논문집
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• 제34권4호
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• pp.119-127
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• 2022

본 연구에서는 테트라포드로 피복된 경사식 마운드 위의 직립벽에 작용하는 충격쇄파압을 쇄파 형태에 따라 구분하기 위해 규칙파를 생성하고 충돌 직전의 유속장과 기포분율을 측정하였다. 유속장 측정을 위해 쇄파 중 발생하는 기포의 움직임을 추적하는 기포영상유속계를 사용하고 기포분율 측정을 위해 복합파고계 기법(Na and Son, 2021)을 활용하였다. 측정된 입사파의 주기가 짧을수록 최대평균유속은 사면에서 파속에 비해 적은 감소율을 보였지만 파랑이 사면을 따라 진행하며 쇄파가 더 빨리 발생하여 기포분율이 증가하였고 결과적으로 중복파압형태의 파압이 작용하였다. 주기가 큰 실험파의 경우 충돌 전 유입되는 공기가 적어 flip-through 형태(Cooker and Peregrine, 1991)의 흐름양상을 보였고, 파압이 급격하게 증가함을 확인할 수 있었다.