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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Investigation of the Effects of High Temperature Aging on the Mechanical Behavior of Lead Free Solders
摘要： Lead free solders are renowned as interconnects in electronic packaging due to their relatively high melting point, attractive mechanical properties, thermal cycling reliability, and environment friendly chemical properties. The mechanical behavior of lead free solders is highly dependent on the operating temperature. Previous investigations on mechanical characterization of lead free solders have mainly emphasized stress-strain and creep testing at temperatures up to 125 °C. However, electronic devices, sometimes, experience harsh environment applications including well drilling, geothermal energy, automotive power electronics, and aerospace engines where solders are exposed to very high temperatures from 125-200 °C. Mechanical properties of lead free solders at elevated temperatures are limited. In this work, we have investigated the mechanical behavior SAC305 (96.5Sn-3.0Ag-0.5Cu) and SAC_Q (SAC+Bi) lead free solders at extreme high temperatures up to 200 °C. Stress-strain tests were performed on reflowed uniaxial specimens at four elevated temperatures (T = 125, 150, 175, and 200 °C). In addition, changes of the mechanical behavior of these alloys due to isothermal aging at T = 125 oC have been studied. Extreme care has been taken during specimen preparation so that the fabricated solder uniaxial test specimens accurately reflect the solder material microstructures present in actual lead free solder joints. High temperature tensile properties of the solders including initial modulus, yield stress, and ultimate tensile strength have been compared. As expected, our results show substantial degradations of the mechanical properties of lead-free solders at higher temperatures. With prior aging, these degradations become even more significant. Comparison of the results has shown that the addition of Bi to traditional SAC alloys improves their high temperature properties and significantly reduces their aging induced degradations.
关键词： Yield Stress,Ultimate Tensile Strength,Stress-Strain Curve,SAC alloy,Modulus,Lead-Free Solder,Aging
更新于2025-09-09 09:28:46
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Membership Function-Weighted Non-Linear Fitting Method for Optical-Sensing Modeling and Reconstruction
摘要： Imprecise measurements present universally due to variability in the measurement error. We devised a very simple membership function to evaluate fuzzily the quality of optical sensing with a small dataset, where a normal distribution cannot be assumed. The proposed membership function was further used as a weighting function for non-linear curve fitting under expected mathematical model constraints, namely the membership function-weighted Levenberg–Marquardt (MFW-LM) algorithm. The robustness and effectiveness of the MFW-LM algorithm were demonstrated by an optical-sensing simulation and two practical applications. (1) In laser-absorption spectroscopy, molecular spectral line modeling was greatly improved by the method. The measurement uncertainty of temperature and pressure were reduced dramatically, by 53.3% and 43.5%, respectively, compared with the original method. (2) In imaging, a laser beam-profile reconstruction from heavy distorted observations was improved by the method. As the dynamic range of the infrared camera increased from 256 to 415, the detailed resolution of the laser-beam profiles increased by an amazing 360%, achieving high dynamic-range imaging to capture optical signal details. Therefore, the MFW-LM algorithm provides a robust and effective tool for fitting a proper physical model and precision parameters from low-quality data.
关键词： non-linear curve fitting,sensing modeling and reconstruction,image reconstruction-restoration,optical-sensing signal processing,laser-absorption spectroscopy
更新于2025-09-09 09:28:46
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Fluorescence-Based Real Time Monitoring and Diagnostics of Recombinant <i>Pichia pastoris</i> Cultivations in a Bioreactor
摘要： This study describes the application of the multivariate curve resolution (MCR) analysis technique for real-time analysis of culture fluorescence during recombinant Pichia pastoris cultivation in a bioreactor. Fluorescence spectra were acquired with an on-line dual excitation wavelength fluorometer and then used to develop a real time MCR-based bioprocess monitoring and diagnostics tool. Initial bioreactor experiments using two similar recombinant antibody secreting P. pastoris cell lines showed significant differences in protein production. To distinguish between the contributions of operating conditions and the specific cell line‘s genetic composition to the observed differences in protein production, the bioreactor experiments were repeated and accompanied by real time MCR analysis. The tests demonstrated high sensitivity of MCR-derived ―pure concentration‖ profiles to growth as well as to initial conditions, thus enabling real-time cultivation process trend diagnostics and fault detection.
关键词： fluorescence,monitoring,Multivariate curve resolution,on-line diagnostics,bioreactor
更新于2025-09-09 09:28:46
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Effect of image processing constraints on the extent of rotational ambiguity in MCR-ALS of hyperspectral images
摘要： Hyperspectral imaging is a way to explore the spatial and spectral information of the different compounds in chemical or biological samples. In addition, multivariate curve resolution alternating least squares (MCR-ALS) can be used to extract this information based on the bilinearity assumption. However, it is well-known that using proper constraints can reduce the amount of uncertainty in the results of MCR, which is called rotational ambiguity. In MCR-ALS analysis of hyperspectral images, different image processing techniques, such as model fitting, image segmentation or sparse image recovery can be applied as spatial constraints. In this contribution, we aim to investigate how the use of these spatial constraints limits the extent of rotational ambiguity of MCR-ALS solutions. For this purpose, we evaluate the extent of rotational ambiguity and use Borgen plots to visualize it. We show on simulations and real hyperspectral imaging data that accuracy of the results is improved when spatial constraints are applied.
关键词： Borgen plot,Uncertainty,Area of feasible solutions,Spatial constraints,Multivariate Curve Resolution - Alternating Least Squares
更新于2025-09-09 09:28:46
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Mechanically induced ferroelectric domain evolution during crack propagation
摘要： Ferroelectric switching in the locality of the crack tip in lead zirconate titanate ceramics leads to a change of both polarization and remanent strain, which affects substantially the stress field and fracture behavior. In particular, for tetragonal crystals the 90? domain reorientation is believed to enhance fracture toughness of the damaged piezoelectric ceramics. Current research models evolution of the domain reorientation processes during crack propagation by a micromechanical model using finite element analysis. The crack growth is numerically simulated by means of electromechanical cohesive elements along the prospective crack path. The study of these unreversible dissipative mechanisms makes the main subject of our numerical investigations. The computed 3D scattering of domain orientations in a mechanically loaded PZT-PIC151 CT-specimen is compared with in-situ X-ray diffraction experiments in synchrotron [1]. It is found that the preferred orientation and intensity of domain distribution in the mechanically loaded specimen depend on the in-plane position and are related to the projected deviatoric stresses/strains. In contrast to simulations with a fixed crack tip [2], during crack propagation the maximal tensile stresses and region of highest intensity of domain reorientation are moved with the crack tip and smeared over a process zone. While the crack length increases, the domain switching belt causes a shielding effect leading to an apparent materials toughening. Such fully coupled, three-dimensional simulation of crack growth resistance curves is the first one in ferroelectrics.
关键词： microstructure,ferroelectric switching,R-curve,fracture mechanisms,transformation toughening
更新于2025-09-09 09:28:46
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald, Germany (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Estimation of Internal Pressure of Vacuum Interrupter by Measuring Partial Discharge Current
摘要： Loss of vacuum in vacuum interrupter (VI) is becoming an interesting theme for VI used in medium voltage range beyond its lifetime of typically 20 – 30 years. The early detection of abnormality in the vacuum insulated equipment must be important for the development of higher voltage vacuum circuit breakers (VCBs), such as cubicle type gas insulated switchgear (C-GIS) with compressed gas and/or insulation gas. In the present study, for the purpose of diagnosing the vacuum pressure in VI by a partial discharge (PD) measurement, PD characteristics in medium vacuum range of 1 Pa to 100 Pa were investigated. As a leakage gas, air was sealed into the VI, and its pressure was regulated from 2.2 Pa to 100 Pa, which corresponds to the left region of Paschen curve. From PD current waveforms by detecting resistor connected to plane electrode outside the VI, the charges, occurrence frequency and phase characteristics of PDs for each applied AC voltage and internal vacuum pressure were determined. It was concluded that a number of occurrence of PD and PD charges would be dominant parameter for determination of the internal pressure of VI.
关键词： Paschen curve,vacuum interrupter,vacuum pressure,partial discharge
更新于2025-09-09 09:28:46
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Electronic Structures of Hydrogen Functionalized Fullerenes: Density Functional Theory (DFT) Study
摘要： In this work, the electronic structures and formation mechanism of hydrogen-functionalized fullerene were investigated by means of density functional theory. The mechanism of the addition of a hydrogen atom to the fullerene surface was mainly investigated. Both pure and boron-nitrogen-substituted fullerenes (denoted by C60 and BNC58, respectively) were examined. We found that the addition of hydrogen atom to B (boron atom) and C (carbon atom) sites of BNC58 proceeded without an activation barrier, whereas the hydrogenation of N (nitrogen atom) sites required activation energy. The electronic states of hydrogen-functionalized C60 and BNC58 are discussed on the basis of these theoretical results.
关键词： Potential Energy Curve,BN-Fullerene,Hyperfine Coupling Constant,Spin Density,Interstellar Reaction
更新于2025-09-04 15:30:14
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Evaluation of the validity of Qraycam for tooth examination during epidemiological surveys
摘要： Objectives: The aim of this study was to evaluate applicability of the Qraycam device for detecting caries and filling body during tooth examinations. Methods: Fifty-two subjects aged 25 to 34 years were recruited for tooth examination. Two examiners (an epidemiologic expert and a non-expert) performed visual tooth examination using only dental operating light, dental mirror, and air-drying without a dental explorer. Pictures or videos of every tooth surface were obtained under visual ray and 405 nm blue ray, respectively, by using Qraycam. The two examiners then evaluated these videos or images more than 7 days after visual examination. Agreement between the two examiners and area under the receiver operating characteristics (ROC) curve (AUC) were evaluated based on the gold standard derived from visual and Qraycam examinations. Results: The results of the visual, visible ray image, and 405 nm blue ray image examinations showed very good kappa agreement with the gold standard for both examiners. The 405 nm blue ray image examination showed higher kappa agreement than visible ray image examination, and was similar to visual examination. Accuracy of detecting caries was enhanced by using 405 nm blue ray images from Qraycam. Accuracy of detecting filling body on 405 nm blue ray image examination was almost same as that by visual examination. Conclusions: Tooth examination with Qraycam images revealed high agreement with the gold standard and showed accuracy for detecting caries and filling body. Therefore, Qraycam would enhance the quality of oral epidemiologic survey including tooth examination and save cost and time of survey.
关键词： Quantitative Light-Induced Fluorescence,Qraycam,Epidemiological tooth survey,Tooth examination,ROC curve
更新于2025-09-04 15:30:14
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The influence of dopants on thermoluminescence of Sr2MgSi2O7
摘要： We report the influence of dopants on the thermoluminescence of Sr2MgSi2O7. Samples studied comprise undoped Sr2MgSi2O7 and doped versions, namely, Sr2MgSi2O7:Dy3+, Sr2MgSi2O7:Eu3+, Sr2MgSi2O7:Tb3+ and Sr2MgSi2O7:Tb3+,Eu3+ phosphors. All samples show a broad glow peak near 60oC when measured at 1 °C/s after irradiation to 10 Gy. The peak changes with partial heating, irradiation and fades between irradiation and measurement in a manner expected of a composite one. The behaviour is used to exemplify the analysis of a composite peak on the basis that particular features reflect those of the dominant component.
关键词： dose response,thermoluminescence,glow curve,phosphor
更新于2025-09-04 15:30:14
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Sodium Doping Effect on Optical Permittivity, Band Gap Structure, Nonlinearity and Piezoelectric Properties of PZT Nano-colloids and Nanostructures
摘要： In this research, effects of sodium atoms doping on optical properties of lead zirconate titanate (PZT) nanoparticles (NPs) are studied and compared with undoped particles. Analyses show formations of PZT nanostructures with dimensions below 30 nm. X-ray diffraction patterns show that the particle size increases and the intensity of the preferred direction decreases as the doping sodium atoms are used in the structure. Analyzing absorption spectra of the colloidal solutions shows doped particles are better absorbers at violet-green region of spectra. Also, it has been concluded that PZT NPs only have indirect optical band gap that is narrower for doped particles. Optical permittivity of the ?lms has been compared using a numerical method and shows the prominent effect of doping on real and imaginary parts of permittivity. Also, z-scan experiments have been done to measure thermo-optical and nonlinear absorption coef?cients of the nano-colloids using continue wave Nd-YAG laser illumination. Finally, sodium doping effects on piezoelectric properties of the samples are investigated using a Michelson interferometer.
关键词： z-scan,Piezoelectric,Michelson interferometer,dispersion curve,PZT nanoparticles
更新于2025-09-04 15:30:14