• Journal of the Microelectronics and Packaging Society
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• v.29 no.3
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• pp.55-61
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• 2022

In this study, properties of Pb-free solder joints which were combined using Sn-3.0Ag-0.5Cu (SAC305) Pb-free solder with a mid-temperature type of melting temperature and Sn-57Bi-1Ag Pb-free solder with a low-temperature type of melting temperature were reported. Combined Pb-free solder joints were formed by reflow soldering processes with ball grid array (BGA) packages which have SAC305 solder balls and flame retardant-4 (FR-4) printed circuit boards (PCBs) which printed Sn-57Bi-1Ag solder paste. The reflow soldering processes were performed with two types of temperature profiles and interfacial properties of combined Pb-free solder joints such as interfacial reactions, formations of intermetallic compounds (IMCs), diffusion mechanisms of Bi, and so on were analyzed with the reflow process conditions. In order to compare reliability characteristics of combined Pb-free solder joints, we also conducted thermal shock test and analyzed changes of mechanical properties for joints from a shear test during the thermal shock test.

• Fire Science and Engineering
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• v.24 no.2
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• pp.38-43
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• 2010

The purpose of this study is to secure the basis for judgment on the cause of an accident by analyzing the melting characteristics of a blade type fuse used for vehicles due to overload. In order to increase the reliability of the test, it was conducted by connecting the electrical system with conditions similar to those of an actual vehicle to apply the load. Carbonization pattern experiment of fuse by outside flame applied Korean Standard (KS). The fuse melted by the overcurrent showed a smooth cross-section while the test terminals, clear plastic body, etc., burnt out by the external flame was badly deformed. When 185% of the rated current (27.8A) was applied to a cable of 15A rated current onto which an over-capacity fuse (20A) was installed, the fuse melting time was 217 seconds. In addition, when a load current of 28.8[A] (139%) was applied, the fuse's test terminal and terminal blade were not burnt out although foam was observed on some parts of the plastic body. When a load capacity of 28.2[A] (141%) was applied to a cable of 15A rated current onto which an over-capacity fuse (30A) was installed, the fuse melting time was approximately 10 seconds. When a load current of 35.8[A] (119%) was applied, the fuse's test terminal and terminal blade were not burnt out, although some parts of the plastic body was swelled. However, it was observed that the switch terminal melted if approximately six minutes lapsed under such conditions. When a load capacity of 39.4[A] (131%) was applied to a cable of 15A rated current onto which an over-capacity fuse (30A) was installed, the fuse melted in approximately 69 seconds, and the test terminal and terminal blade were not burnt.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.53-59
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• 2003

Strain Energy Hinge(SEH) has been used in Korea Multi-purpose Satellite(KOMPSAT) series to deploy the solar panel due to the good record of reliability. However, when it reached a desired deployment position, a large buckling force is applied to the main body. This may cause structural damage and also affect control of the satellite. Therefore, reliable dynamic analysis for the deployment system is required at a design stage. Moreover, various mission of a satellite has made the size of solar panels got bigger, so elastic effect has to be considered seriously to get more precise analysis results. In this paper, a dynamic analysis method to predict the deployment is verified by KOMPSAT-2 deployment test.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.103-114
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• 2023

Monitoring the site of an underground construction wall is crucial to confirm the stability of the supports and ground due to excavation. In particular, it is essential to maintain the accuracy of a load cell gauge, which identifies the load of the support transmitted from the excavated ground. However, research on verification methods and regulations that can identify the accuracy of load cell gauges at construction sites is inadequate, which is a problem as load cell gauges are installed without proper performance inspections. In this study, performance tests were conducted by a complete investigation of load cell gauges sold in Korea and comparing them with foreign products to determine defect causes. In addition, the criteria for selecting a load cell gauge were presented, and the results of this study were considered to help select a highly reliable load cell gauge.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.8
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• pp.1103-1109
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• 2021

ECS is a control device so that the warship can perform the mission stably by controlling and monitoring the entire propulsion system. As the recent provisions of the warship, it's propelling system is complicated than past, as the demand performance and mission of the warships are diverse. In accordance with the complicated propulsion system configuration, the demand for automatic control function of the ECS is increasing for convenient and stable propulsion system control for convenient and stable. As a result, verification of ECS stability and reliability is required. In this paper, we develop an interlocking signal simulator for verifying ECS control logic and communication protocol for warship with CODLOG propulsion systems. The simulator developed was implemented to simulate a signal of gas turbine, propulsion motors, diesel generator and 11 kinds of auxiliary equipment. The reliability of ECS was verified through the ECS communication program and the I/O signal static test with the simulator.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.175-181
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• 2003

In this reseach, a seepage test is carried out for three kinds of soil using a upward seepage equipment. Reliability about the existing method of pipining investigation were verified making an estimate of the critical velocity, the critical hydraulic gradient, and hydraulic conductivity and so on. Also, sensitive analyses were carried out using Plaxis that is FEM Program about design factors of scour. The height of core had a big infulence on the hydraulic gradient of the embankment's lower part in the result of sensitive anaylsis. Also, second only to the height of core, and the slope of embankment, the width of crest had influence on scour. However, the change of hydraulic gradient in the effluent gateway had a little influence on the crest width of core. Using these results of sensitive analysis on designing, hydraulic gradient in the effluence gateway turned out to be reducing by altering design factors that change of sensitiveness is big, in case of the hydraulic gradient bigger than the standard hydraulic gradient.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.4
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• pp.361-368
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• 2015

Recently, the earthquake has been increasing a lot, damage of electric power facility has been serious as well. Nowadays, the importance of pipe support system such as Hanger, Brace, Snubber connecting the main structure have been emphasized. These devices can prevent pipe from damage so that reduce the vibration and shock acting on the pipe. For this reason, the FCD(Friction Concave Damper) was developed and has been expected to reduce the vibration on the pipe through the Friction Pendulum System. This paper was described the introduction of self-developed mechanical damper using the friction pendulum principle and the characteristic test was performed to verify the performance of the device. Additionally the test results have been compared with predicted F.A.P(FCD Analysis Program-self developed) results. As a result, reliability of design could be improved.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.1053-1060
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• 2013

The purpose of this study is to estimate the packing friction of power-operated valve in nuclear power plants. The roll of packing in valve is preventing leakage through stem. Packing friction is highly depend on gland nut tightness which means higher reliability in sealing is lower operability. For the estimation of friction, we used statistical analysis and experimental analysis. In experimental approach, we have performed packing fY test and applied it to valve field test. In statistical approach, we have used 10 years DB of safety-related valve in nuclear power plant and analyzed packing friction based on confidence interval of sample. The comparison of two results shows that statistical analysis for packing friction are more accurate than fY analysis even though both approach have error compared to measured value but we confirmed that statistical approach is proper way to estimate packing friction.

• Journal of Energy Engineering
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• v.21 no.3
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• pp.243-248
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• 2012

In this study, The report analysed the characteristics of power drop and damage of surface in solar cell through high temperature and humidity test. The solar cells were tested during the 1000hr in $85^{\circ}C$ temperature and 85% humidity conditions, that excerpted standard of PV Module(KS C IEC-61215). An analysis of the cell surface through EL(Electroluminescence), the cell has partly change of surface in yearly. Single-crystalline Solar cell efficiency is decreased from 17.7% to 15.6% and decreasing rate is 11.9%. On the other hand, Poly-crystalline Solar cell efficiency is decreased from 15.5% to 14.0% and decreasing rate is 9.3%. A comparison of the fill factor for analysis of electro characteristic in yearly, Single-crystalline Solar cell efficiency is decreased from 78.7% to 78.1% and decreasing rate is 4.7%. On the other hand, Poly-crystalline Solar cell efficiency is decreased from 78.1% to 76.7% and decreasing rate is 1.8%. Single-crystalline has more bigger power drop than poly-crystalline by the silicon purity and silicon atom arrangement. Also, FF decreasing rate has more bigger drop than efficiency decreasing rate for the reason that the damage of surface by exterior environmental factor is the more influence in cell than other reason that is decreasing FF by damage of p-n junction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.169-179
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• 2010

Satisfying the same probability of loss of control and essentially two fail operative performance with a triplex computer architecture requires a lot of modification of the conventional redundancy management design techniques, previously employed in quadruplex digital flight control computer. T-50 FCS for triplex redundancy management design applied an advanced digital flight control architecture with an I/O controller which is functionally independent of the digital computer to achieve the same reliability and special failure analysis and isolation schemes for fail operational goals with a triplex configuration. The analysis results indicated that the triplex flight control system is to satisfy the safety requirement utilizing the advanced flight control techniques and the system performance of the implemented flight control system was verified by failure mode effect test.