• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.101-105
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• 2019

The adhesion reliability of the epoxy molding compound (EMC) and the printed circuit board (PCB) interface is critical to the quality and lifetime of the chip package since the EMC protects PCB from the external environment during the manufacturing, storage, and shipping processes. It is necessary to measure adhesion energy accurately to ensure product reliability by optimizing the manufacturing process during the development phase. This research deals with the measurement of EMC/PCB interfacial adhesion energy of chip package that has warpage induced by the coefficient of thermal expansion (CTE) mismatch. The double cantilever beam (DCB) test was conducted to measure adhesion energy, and the spring back force of specimens with warpage was compensated to calculate adhesion energy since the DCB test requires flat substrates. The result was verified by comparing the adhesion energy of flat chip packages come from the same manufacturing process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.53-62
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• 1992

Material can be degraded by using it for a long service under the high temperature and pressure circumstances, Therefore, material degradation can affect the strength of mechanical structures. At present, the life prediction of the degraded structures is considered as an important technical problem. In this paper, the degraded 21/4Cr-lMo steel is the material used for about 10 years around 400.deg. C in an oil refinery plant. The recovered one was prepared out of the above degraded steel by heat treatment for one hour at 650.deg. C. The degradation effect was investigated through the tension test, Hardness test and Charpy impact test. On the smooth surface material, the fatigue crack initiation, growth and coalescence stages of the distributed small cracks were investigated with photographs, and the crack length and density were measured. The measuring results were analyzed by quantative and statistical methods.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.501-507
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• 2017

When zenor diode load current is necessary to be controlled by input voltage as a circuit load, existing voltage controlling method cannot be applied to it because the output current of zenor diode is changed due to breakdown voltage variations. We propose input voltage controlled output current source regardless of zenor breakdown voltage variation due to degradation resulted from severe current applied electronic component life test as a circuit load in this paper. We show breakdown voltage characteristics of this zenor diode circuit through simulation, applying adequate values for each component in order to verify the circuit composed of that method, and then show the result in which output current is controlled by input voltage. We confirmed the output current varies proportional to input voltage, and developed circuit shows a constant value independent of zenor diode breakdown voltage variations due to component degradations.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.176-176
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• 2011

경사 코팅법은 증발 물질이 기판에 수직으로 입사하는 기존 코팅방법과 다르게 증발물질이 기판과 $90^{\circ}$ 이하의 경사각으로 입사하도록 하여 코팅하는 방법이다. 이러한 경사 코팅법은 각도를 달리함으로 인해 비스듬한 기둥, 나선형, C-형, S-형, zigzag 구조 등의 정교하고 폭넓은 박막을 형성 할 수 있다. 이러한 경사 코팅법은 경사굴절 광학필터, 선형 편광 등의 광 산업계에서 널리 사용되고 있다. 본 연구에서는 경사 코팅법을 이용하여 마그네트론 스퍼터링법으로 Al 박막을 제조하였고 다양한 경사 각도에 따른 조직의 특성과 내식성 등을 평가하고 비교하였다. 기판을 $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $90^{\circ}$의 다양한 각도로 위치시켜 냉연강판 및 Si 웨이퍼에 단일층 또는 다층으로 Al 박막을 코팅하였다. 박막의 구조를 확인하기 위해 전자현미경(SEM)을 사용하였으며 기판의 위치에 따른 변화를 관찰하기 위해 시편을 좌, 우, 중간으로 구분하여 분석하였다. Al 박막이 단층일 경우 회전각도 $60^{\circ}$에서 치밀한 조직이 관찰되었으며 이것은 표면의 반사도와 표면조도 결과와도 유사하게 나타났다. 다층 박막에서는 회전각도 $45^{\circ}$에서 아주 치밀한 조직이 나타났으며, $3{\mu}m$ 두께로 코팅한 시편의 염수분무 시험 결과 120시간 경과 후에도 적청이 발생하지 않았다. 이것은 기존의 방법이 약 72시간에서 적청이 발생하는 것과 비교할 때 경사 코팅법으로 코팅된 시편의 내식성이 현저히 향상됨을 나타낸다. 따라서 반응성이 높고 쉽게 산화가 일어나는 철강제품의 부식 방지를 위해 경사 코팅법으로 Al 박막을 제조한다면 치밀한 조직으로 인해 얇은 두께에서도 부식이 발생하는 시간을 연장시켜 제품의 내구수명을 연장시킬 수 있을 것으로 기대된다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.110-110
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• 2018

여러 니켈합금 중 인코넬 600은 원전 가압경수로(PWR)의 튜브 재료로 널리 사용되는 재료이다. 스테인리스강과 비교하여 우수한 내식성과 기계적 특성으로 인해 화학설비, 발전설비, 그리고 해양설비 등과 같은 여러 산업분야에서도 널리 사용되고 있다. 그러나 가압경수로용 증기 발생기의 튜브 재료와 같은 특수 환경에서 예민화에 따른 입계부식 및 입계응력부식 등의 문제가 흔히 보고되고 있다. 이러한 내구성 문제는 설비 및 장비의 수명, 내구성 그리고 안정성 등의 치명적인 영향을 미친다. 따라서 용접, 열처리, 그리고 가공과정에서 발생하는 Inconel 600의 예민화 및 입계부식에 관한 연구가 활발히 진행되고 있다. 그러나 100시간 이상 장시간 열화된 시편에 대한 예민화 연구는 전무한 실정이다. 본 연구에서는 장시간 열화된 Inconel 600의 예민화를 평가하기 위해 최대 1,000시간까지 열화를 실시하였으며, 이에 대한 평가방법으로 Double-Loop Electrochemical Potentiokinetic Reactivation(DL-EPR) 시험법을 적용하였다. 본 실험에서 사용된 인코넬 600의 화학성분(wt, %)은 0.01 C, 0.05 Si, 0.14 Mn, 15.3 Cr, 0.5 Cu, 0.015 S, 그리고 나머지는 Ni 이다. 예민화 평가를 위한 등온 열화는 전기열처리로를 이용하여, $550^{\circ}C$와 $650^{\circ}C$에서 최대 1000시간까지 실시하였다. 열화에 따른 미세조직 변화는 scanning electron microscope와 energy dispersive x-ray spectroscopy를 이용하여 실시하였다. DL-EPR 실험은 $25^{\circ}C$의 0.1M $H_2SO_4$ + 0.001M KSCN(potasium thiocyanate) 수용액 하에서 실시하였으며, 분극은 OCP로부터 600 mV(SSE vs.)까지 1.67mV/s 주사속도로 forward scan을 실시 후, 동일한 속도로 OCP까지 reverse scan을 실시하였다. Degree Of Sensitization(DOS)값은 anodic scan peak($I_a$) 값과 reverse scan peak($I_r$) 값의 비로 산출하였다. $$i.e.\;DOS=I_r/I_a{\times}100$$. 그 결과, 온도 변수에 따른 Inconel 600강의 예민화 거동은 서로 상이한 경향을 나타내었다. $550^{\circ}C$의 경우, 열화가 진행됨에 따라 DOS값은 급격하게 증가하는 경향을 나타냈다. 반면, $650^{\circ}C$에서는 일정시간 이후부터 Cr 확산 현상에 의한 탈 예민화 현상이 관찰되었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.592-598
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• 2017

The purpose of this study is to suggest a new inspection period of ${\triangle}{\triangle}$ guided missiles by analyzing their reliability using field data. The ${\triangle}{\triangle}$ guided missile has an inspection period of five years which was determined using prediction data during its development process. However, from the analysis of its field data, it was shown that the inspection period could be extended to more than 18 years. Based on this result, a policy is proposed to reevaluate the inspection period by means of practical reliability tests.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.5
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• pp.450-457
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• 2009

Periodical thermal shock can introduce defects in thermal barrier coating made by layers of CoNiCrAlY bond coating(BC) and $ZrO_2-8wt%Y_2O_3$ ceramic top coating(TC) on Inconel-738 substrate using plasma spraying. Thermal shock test is performed by severe condition that is to heat until $1000^{\circ}C$ and cool until $20^{\circ}C$. As the number of cycle is increased, the fatigue by thermal shock is also increased. After test, the micro-structures and mechanical characteristics of thermal barrier coating were investigated by SEM, XRD. The TGO layer of $Al_2O_3$ is formed between BC and TC by periodical thermal shock test, and its change in thickness is inspected by eddy current test(ECT). By ECT test, it is shown that TGO and micro-crack can be detected and it is possible to predict the life of thermal barrier coating.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.27-35
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• 2021

Generally, a proper evaluation method of the aging phenomenon of PV modules is required as the electrical performance and lifespan of PV modules can degrade significantly due to several environmental factors, while they are generally known as devices that are used semi-permanently for more than 20 years. On the other hand, there is a lack of objectivity in the existing evaluation method of the aging phenomenon, which compares the adjusted PV output based on STC with the initial PV module specifications due to the data distortion while adjusting the measured data. Therefore, this study implemented a test device for an aging diagnosis to measure and collect actual data from a PV module section and modeled the data for aging using MATLAB S/W to minimize the variability of the PV output, communication error, and delay. Furthermore, this study confirmed the usefulness of the presented test device for aging diagnosis of the PV modules by diagnosing the total period and yearly-basis degradation rate of aging PV modules as 25.73% and 1.55%, respectively, according to the on-site output characteristics of the PV modules by season.

• International Journal of Highway Engineering
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• v.8 no.3 s.29
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• pp.105-114
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• 2006

A popular alternative to extend the life of aged pavement is asphalt overlay. However, it has a very serious and inherent shortcoming in deterring a reflection crack. Although joint-rehabilitation and stress-relief techniques have been applied to deter such reflection cracks in aged pavement, the techniques had a limited success only in slowing down the progress of a reflection crack. Rubblization technique rubblizes the concrete pavement slab in situ and uses the rubblized slab as the base material. Then, pavement overlay is applied to finish off the rehabilitation of aged pavement. This rubblization technique has the advantage of solving the problem of reflection cracking completely. When rubblization technique is applied, the upper layer of aged concrete pavement is rubblized between 40mm-70mm in depth. However, the lower layer is typically rubblized more than 100mm in depth. Nevertheless, it is difficult to turn the entire concrete pavement of more than 30cm in depth into rubblized aggregate of appropriate size. Thus, a simulation experiment was carried out to find the appropriate rubblized depth, which avoids the reflection cracking and still maintains the function of subbase, by varying the depth of rubblized depth in loom increments of 0cm, 10cm, and 20cm. The result indicated the optimum rubblized depth was 10cm (Lee, 2006). Additionally, a small rubblizinge equipment was developed in order to derive the rubblization technique appropriate for thick concrete pavement. This equipment was tested out on an experimental pavement, which was constructed with the same standard and specification for the road in actual use, by varying its rubblizing head shape and energy as well as the effective area of rubblization. This experiment led to a prototype equipment for rubblization of thick concrete pavement. The prototype was put into use on a highway, undergoing a test construction and monitoring afterwards. This entire process was necessary for the validation of the proposed rubblization technique.

• Journal of Conservation Science
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• v.31 no.2
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• pp.131-145
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• 2015

Cultural assets restoration is being considered highly as a practical way to extend the lifespan of damaged cultural assets and re-highlight their value. However, restoration process has been mostly dependent on the manual work involving the experience and skill of a person performing restoration, thereby requiring much time and effort. In recent, it became possible to apply a method allowing restoration to be performed more accurately and easily according to the material characteristics and shape of cultural assets. Namely, it is to use a method of printing out the 3D shape data computed in computer as real object by using 3D printer for the restoration that has been performed manually. The missing part of a cultural asset is computed into computer data first and is printed out by using 3D printer to undergo a simple shaping process. The result of 3D printer application showed that repetitive output and shape and figure revision of digital data were possible, and it was possible to improve the degree of completedness of restoration through test output using various types of restoration materials using various materials. For the purpose of verifying the possibility of applying 3D printer to restore missing part of earthenware, two pieces of modern reproductions, namely, the Seven Treasure Incense Burner and Earthenware with Wagon Wheel Decoration, were artificially damaged. The restoration result showed that compared to manual work, it showed better effectiveness in curtailing work time and reproducing accurate shape. On the other hand, secondary manual work was slightly needed for detailed binding and to vividly express surface texture.