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Daeil Kwon,Azarian, Michael H.,Pecht, Michael IEEE 2015 IEEE transactions on components, packaging, and ma Vol.5 No.11
<P>Solder joints are among the most common failure sites in electronic assemblies. This paper presents a prognostic approach that allows for the remaining useful life prediction of solder joints using an RF impedance analysis and the Gaussian process (GP) regression. While the solder joints were exposed to a mechanical stress condition to generate fatigue failures, the RF impedance of the solder joint was continuously monitored. The RF impedance provided an early indication of the impending solder-joint failure in the form of a gradual increase prior to the end of life. A GP model was applied to the RF impedance obtained from the fatigue tests in order to estimate the remaining life of the solder joint in real time. It was demonstrated that the GP model successfully predicted the time to failure of the solder joint with high accuracy prior to failure. The prediction performance was also evaluated using prognostic metrics.</P>
Integrated Vehicle Mass Estimation Using Longitudinal and Roll Dynamics
Daeil Kim,Seibum B. Choi,Jiwon Oh 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10
Information of vehicle mass is crucial for vehicle safety control. Vehicle mass value is treated as a constant value for ESP(Electronic Stability Program) and other vehicle safety controls, but it varies with the number of passengers or the weight of load vehicle carries. This paper suggests an integrated mass estimation algorithm based on a recursive least square method and parameter adaptation. First, using the longitudinal dynamics and recursive least square method, the mass estimation algorithm is designed. Second, two sorts of mass estimation algorithms are designed using the roll dynamics. The first algorithm is designed using adaptation law from roll angle observer and Lyapunov stability analysis and the second algorithm is designed using recursive least square method. Then, mass estimation algorithm is finally integrated with two algorithms to estimate vehicle mass for all sorts of situations. The simulation results through CarSim and Matlab/Simulink show the performance of the proposed vehicle mass estimation algorithm.
Effect of the Cu Bottom Layer on the Optical and Electrical Properties of In₂O₃/Cu Thin Films
Daeil Kim(김대일) 한국진공학회(ASCT) 2011 Applied Science and Convergence Technology Vol.20 No.5
유리 기판 위에 RF와 DC 마그네트론 스퍼터링 방법으로 100 ㎚ 두께의 In₂O₃ 단층 박막과 In₂O₃ 100 ㎚/Cu 3 ㎚의 두께를 갖는 적층박막을 증착하고, 구리 기저 층 증착에 따른 상부 In₂O₃ 박막의 광학적, 전기적 특성의 변화를 연구하였다. 상온에서 증착 된 In₂O₃ 박막의 가시광 투과도와 면 저항은 79%와 2,300 Ω/□이었다. 구리 기저 층의 광 흡수에 의하여, In₂O₃/Cu 적 층박막의 가시광 투과도는 71%로 감소하였으나, 면 저항은 110 Ω/□로 측정되어 상대적으로 우수한 전기적 특성을 구할 수 있었다. 본 연구에서 Figure of Merit 분석을 통하여 구리 기저 층이 상부 In₂O₃ 투명전극의 전기적, 광학적 특성을 개선 할 수 있음을 확인하였다. Indium oxide (In₂O₃) single layer and In₂O₃/copper (Cu) bi-layer films were prepared on glass substrates by RF and DC magnetron sputtering without intentional substrate heating. In order to determine the effect of the Cu bottom layer on the optical, electrical and structural properties of In₂O₃ films, 3-㎚-thick Cu film was deposited on the glass substrate prior to deposition of the In₂O₃ films. As-deposited In2O3 films had an optical transmittance of 79% in the visible wavelength region and a sheet resistance of 2,300 Ω/□, while the In₂O₃/Cu film had optical and electrical properties that were influenced by the Cu bottom layer. In₂O₃/Cu films had a lower sheet resistance of 110 Ω/□ and an optical transmittance of 71%. Based on the figure of merit, it can be concluded that the Cu bottom layer effectively increases the performance of In2O3 films for use as transparent conducting oxides in flexible display applications.
A model-based prognostic approach to predict interconnect failure using impedance analysis
Daeil Kwon,Jeongah Yoon 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.10
The reliability of electronic assemblies is largely affected by the health of interconnects, such as solder joints, which provide mechanical, electrical and thermal connections between circuit components. During field lifecycle conditions, interconnects are often subjected to a DC open circuit, one of the most common interconnect failure modes, due to cracking. An interconnect damaged by cracking is sometimes extremely hard to detect when it is a part of a daisy-chain structure, neighboring with other healthy interconnects that have not yet cracked. This cracked interconnect may seem to provide a good electrical contact due to the compressive load applied by the neighboring healthy interconnects, but it can cause the occasional loss of electrical continuity under operational and environmental loading conditions in field applications. Thus, cracked interconnects can lead to the intermittent failure of electronic assemblies and eventually to permanent failure of the product or the system. This paper introduces a model-based prognostic approach to quantitatively detect and predict interconnect failure using impedance analysis and particle filtering. Impedance analysis was previously reported as a sensitive means of detecting incipient changes at the surface of interconnects, such as cracking, based on the continuous monitoring of RF impedance. To predict the time to failure, particle filtering was used as a prognostic approach using the Paris model to address the fatigue crack growth. To validate this approach, mechanical fatigue tests were conducted with continuous monitoring of RF impedance while degrading the solder joints under test due to fatigue cracking. The test results showed the RF impedance consistently increased as the solder joints were degraded due to the growth of cracks, and particle filtering predicted the time to failure of the interconnects similarly to their actual timesto-failure based on the early sensitivity of RF impedance.