共查询到20条相似文献,搜索用时 15 毫秒
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Whisker growth on tin finishes of different electrolytes 总被引:2,自引:0,他引:2
Whisker growth on tin finishes produced by three different plating baths (sulfate-based, alkaline stannate-based and stannous chloride-based) was observed by both optical and scanning electronic microscopy (SEM), the results showed that whisker growth on the finish plated by alkaline stannate bath is easier and faster than that on the finish plated by sulfate-based bath or stannous chloride-based bath. Furthermore, the alkaline stannate bath showed the lowest cathode current efficiency, and micro-nodules were observed after plating when using this bath. The reason for alkaline stannate bath to promote whisker growth is also discussed. 相似文献
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In this paper Monte Carlo simulation results of step stress tests are analyzed. It considers the Weibull distribution as the model of constant stress, and as acceleration model the Inverse Power Law. Simulated regular and irregular ladders results are compared from the point of view of the precision of the calculated values and the time consumption of the tests.It is concluded that the use of adequate irregular ladders enables design improvement of step stress tests. 相似文献
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This paper considers ramp tests for Weibull life distribution when there are limitations on test stress and test time. The inverse power law and a cumulative exposure model are assumed. Maximum likelihood estimators of model parameters and their asymptotic covariance matrix are shown. The optimum ramp test plans are given which minimize the asymptotic variance of the ML estimator of a specified quantile of log(life) at design constant stress. The effects of the pre-estimates of design parameters are studied 相似文献
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Some key results of a benchmark test, initiated in 1992 by the Working Group 2 of COST Project 240 at a modelling workshop in Teupitz, Germany, are presented. A great number of BPM algorithms, such as the FTBPM, various types of FDBPMs, wide angle approximations and adaptive FE-BPM are compared. The quasi-analytic character of the benchmark tests gains a deeper insight into the absolute accuracy 相似文献
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Fukuda Y. Osterman M. Pecht M. 《Electronics Packaging Manufacturing, IEEE Transactions on》2007,30(1):36-40
The global movement to lead-free electronics has led semiconductor device assemblers to switch terminals and finishes from lead-based to pure tin or high tin lead-free alloys. This transition has resulted in a reliability concern associated with the formation of conductive tin whiskers, which can grow from a device terminal or lead and cause current leakage or short circuits. This paper presents the results of an experimental study on tin whisker growth. Test specimens consisted of matte and bright tin finishes on copper, Alloy-42, and brass substrate materials. The heat treatments included annealing and two types of simulated reflow. Maximum whisker length and whisker density were measured on 24 different types of tin-plated specimens, after three, eight, and 16 months of room ambient storage after various heat treatments 相似文献
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The diagnosis of coronary artery disease (CAD) is an important task in the management of cardiology patients. Recently, the use of pharmacological stress testing has become available as an alternative to exercise stress testing (ETT). A new system (device-drug combination) was developed specifically for the diagnosis of coronary artery disease. The system uses a novel catecholamine, arbutamine, which is infused intravenously to increase heart rate (HR) and cardiac contractility in order to evoke signs of ischemia. The development of a closed-loop control algorithm for the delivery of this drug and a pharmacodynamic (PD) model representing the HR response to arbutamine infusions are presented. Model parameters are estimated from clinical data on normal volunteers and patients. Based on this mathematical model, a rule-based control algorithm is designed. The structure of the control algorithm is discussed and testing of the algorithm based on simulations and animal and human trials are summarized. Results from clinical trials shows that the algorithm controls the HR increase according to a selected trajectory. The automated delivery of the drug can provide the cardiologist with an efficient, effective, and safe method for administering a pharmacological stress test 相似文献
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Jing Cheng Fuqian Yang Paul T. Vianco Bei Zhang James C.M. Li 《Journal of Electronic Materials》2011,40(10):2069-2075
By depositing different thicknesses of Sn films over a silicon wafer precoated with Cr and Ni adhesion layers and then by
bending the tinned wafer using a dead load applied at the center to introduce the same compressive stresses in the Sn films,
the growth rate of whiskers appeared to have a maximum for a certain thickness. This is explained by assuming the Sn atoms
to flow along the vertical grain boundaries (perpendicular to the interface) into the interface between Sn and Ni and then
along the interface to the root of the whisker through some more vertical grain boundaries. The resistance along the vertical
grain boundaries appeared to control the rate of whisker growth for thick films. 相似文献
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当电子工业中完全实现无铅化时,晶须问题成为新的悬念。关于Sn晶须的成长机理和抑制方法的研究已经遍及全世界。晶须发生和成长被认为是Sn镀层上的压缩应力引起的。晶须分为内部和外部应力型。文章通过压缩负荷试验研究了外部应力型晶须的抑制方法。这种方法是Sn表面镀层和Cu上的Ni基底镀层之间介入薄Au镀层。结果发现镀Sn以后不久就形成了金属间化合物AuSn4,Au镀层有效地减轻了Sn晶须的数量,缩短了Sn晶须的长度。 相似文献
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Marco Secondini Simon Rommel Gianluca Meloni Francesco Fresi Enrico Forestieri Luca Potì 《Photonic Network Communications》2016,31(3):493-502
Nonlinearity mitigation based on the enhanced split-step Fourier method (ESSFM) for the implementation of low-complexity digital backpropagation (DBP) is investigated and experimentally demonstrated. After reviewing the main computational aspects of DBP and of the conventional split-step Fourier method (SSFM), the ESSFM for dual-polarization signals is introduced. Computational complexity, latency, and power consumption of DBP based on the SSFM and ESSFM algorithms are estimated and compared. Effective low-complexity nonlinearity mitigation in a 112 Gb/s polarization-multiplexed QPSK system is experimentally demonstrated by using a single-step DBP based on the ESSFM. The proposed DBP implementation requires only a single step of the ESSFM algorithm to achieve a transmission distance of 3200 km over a dispersion-unmanaged link. In comparison, a conventional DBP implementation requires 20 steps of the SSFM algorithm to achieve the same performance. An analysis of the computational complexity and structure of the two algorithms reveals that the overall complexity and power consumption of DBP are reduced by a factor of 16 with respect to a conventional implementation, while the computation time is reduced by a factor of 20. Similar complexity reductions can be obtained at longer distances if higher error probabilities are acceptable. The results indicate that the proposed algorithm enables a practical and effective implementation of DBP in real-time optical receivers, with only a moderate increase in the computational complexity, power consumption, and latency with respect to a simple feed-forward equalizer for bulk dispersion compensation. 相似文献
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Security risk mitigation is a salient issue in systems development research. This paper introduces a lightweight approach
to security risk mitigation that can be used within an Agile Development framework — the Security Obstacle Mitigation Model
(SOMM). The SOMM uses the concept of trust assumptions to derive obstacles and the concept of misuse cases to model the obstacles.
A synthetic scenario, based on an on-line system, shows how the SOMM is used to anticipate malicious behaviour with respect
to an operational information system and to document a priori how this malicious behaviour should be mitigated. Since the SOMM is conceptually simple in deployment, its use is well within
the capacities of the users who form part of an Agile Development team and crucially it should not take up a significant amount
of development time. 相似文献
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Tin Whisker Growth on the Surface of Sn-0.7Cu Lead-Free Solder with a Rare Earth (Nd) Addition 总被引:1,自引:0,他引:1
The phenomenon of rare earth (RE) additions inducing whisker growth in Sn-0.7Cu-Nd (0.1–5 wt.%Nd) solder is reported. The
results showed that Nd exists as Sn3Nd in the microstructure of the solder alloys. A snowflake-like Sn3Nd was observed when Nd ≤ 0.5 wt.%. After exposure to ambient conditions, the Nd-bearing alloys have a strong tendency toward
whisker growth, with a short incubation time for whisker nucleation (only several hours). All whiskers originated from the
Sn-Nd compound, where whiskers grew relatively fast; the average growth rate of the five longest whiskers was approximately
4 ?/s, and a 190 μm whisker was observed within 480 h. Based on these results, it was predicted that whisker growth would be inevitable for
all RE-bearing solders. The cause of this phenomenon is also discussed. Finally, the authors suggest that any solders doped
with RE should be carefully considered again. 相似文献
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Fei Xiang Guisheng Liao Cao ZengWeiwei Wang 《AEUE-International Journal of Electronics and Communications》2013,67(10):839-847
A novel technique for mitigating the multipath-induced code delay estimation error in Global Positioning System (GPS) is proposed. In contrast to conventional methods that aim to eliminate multipath signals, the proposed method exploits them to enhance the direct signal without affecting the accuracy of GPS code delay estimates. To achieve this, coherent accumulation of the received GPS signals is first done by transforming the received data into frequency domain and the parameters of multipath signals are then estimated by sparse reconstruction algorithm. Subsequently, a modified local reference signal is employed in delay lock loop (DLL) of the GPS receiver, which mitigates the pseudo-range estimation error and increases the correlation value of direct GPS signal. Simulation results demonstrate the performance and robustness of the proposed method. 相似文献
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This paper addresses the problem of interference mitigation in cooperative Space Time Block Coded Orthogonal Frequency Division
Multiplexing (STBC-OFDM) systems in the presence of asynchronism. This scheme first preprocesses the received ST codewords
to convert the equivalent fading matrix into a suboptimal ordering upper triangular form based on low complexity permutation
QR decomposition, and then suppresses the InterCarrier Interference (ICI) and InterSymbol Interference (ISI) by exploiting
Successive Interference Cancellation (SIC) technique. Simulation results show that the performance of the proposed algorithm
slightly outmatches or asymptotically approaches to that of the existing Minimum Mean Square Error (MMSE) detector depending
on the magnitude of the Carrier Frequency Offsets (CFOs) but with less complexity. 相似文献
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As the industry moves toward lead-free electronics, a replacement for the traditional tin-lead plating is required. Pure tin is the coating of choice for many suppliers, but there is a well-known problem with the growth of tin whiskers. A whisker is comprised of a tin crystal which, after an incubation period, grows with time. Whiskers may grow long enough to cause shorts in electronic circuits. A test method is required for evaluating the reliability risk inherent in tin whiskers. The Japanese government requested the Japan Electronics and Information Technology Industries Association (JEITA) to establish test methods for solderability, reliability, whisker, and migration for lead-free electronics. The goal of this subcommittee was to propose the test methods for tin whiskers by March 2004. The committee carried out a literature survey, and developed hypotheses for whisker growth, which was then applied to test methods. Two types of studies were undertaken. One is a fundamental study to verify the hypothesis. The other looked at accelerated tests to develop recommended test conditions. As a result, we found that the diffusion of copper, oxidation, and thermal cycling all influence tin whisker growth. This paper describes the results of the fundamental studies and reports on the JEITA whisker growth mechanism. 相似文献