Effects of solid-state annealing on the interfacial intermetallics between tin-lead solders and copper

The interfacial intermetallics between Cu and solder were studied for four Sn-Pb compositions at the annealing temperatures of 125°C, 150°C, and 175°C for up to 30 days. The η-phase (Cu₆Sn₅) layer formed during reflow continues to grow during annealing. An additional layer of ɛ-phase (Cu₃Sn) forms at the η/Cu interface after an incubation annealing time. The thickness results fit a power-law relationship against time with average exponents 0.69 and 0.44 for the η phase and the ɛ phase, respectively. On prolonged annealing, the proportions of the individual phases in the total layer reach a steady state.     

可靠性预计模型的参数敏感度分析

利用蒙特卡罗仿真 ,对可靠性预计模型中的主要参数例如温度、电应力、元器件构成比例、环境系数、质量系数等等 ,对设备可靠性预计值的影响程度进行了分析 ;比较了不同手册的参数预计参数敏感度 ;对可靠性设计中应注意的问题提出了建议。     

单片机系统中数据存储的可靠性研究

详细介绍了影响单片机系统数据存储可靠性的原因,从硬件和软件两个方面阐述了提高单片机系统数据存储可能性的具体方法。     

一种基于时频分析的语音卷积信号盲分离算法

本文根据语音信号在实际环境下传播存在多径效应而造成反射信号之间产生时延差异的特点,提出了一种新的基于卷积混合矩阵模型的盲分离算法.该算法利用语音信号频谱中普遍存在的稀疏特性,通过对两路接收信号语谱图的对比分析估计出模型中时延参数和幅度系数的待定值;更进一步,从极大似然估计的思想出发,构造了一种基于时延参数和幅度系数的可信度函数,提出了通过寻找上述可信度函数的峰值以准确确定混合矩阵参数的方法.与现有的基于独立性假设的盲分离算法不同,本算法利用了语音信号频谱中普遍存在的稀疏特性,适用于求解大多数场合下的盲源分离问题.由于本算法本质上是一种非迭代的算法,且不存在发散的问题,故具有快速、稳定的特点.仿真实验和实际环境下所得到的实验结果表明,该算法能在各种信噪比的条件下准确地估计出由环境所确定的时延和幅度参数,并据此成功地分离出源语音信号,是一种面向真实环境下语音盲分离应用的有效算法.     

Improved Reliability‐Based Iterative Decoding of LDPC Codes Based on Dynamic Threshold

A serial concatenated decoding algorithm with dynamic threshold is proposed for low‐density parity‐check codes with short and medium code lengths. The proposed approach uses a dynamic threshold to select a decoding result from belief propagation decoding and order statistic decoding, which improves the performance of the decoder at a negligible cost. Simulation results show that, under a high SNR region, the proposed concatenated decoder performs better than a serial concatenated decoder without threshold with an E_b/N₀ gain of above 0.1 dB.     

船载AIS无线传输系统的软硬件可靠性设计

船舶自动识别识别系统(AIS)是一种新型的助航系统和设备,在海事通信中将会发挥着巨大的作用.无线传输系统是该系统中底层的重要组成部分.为了使无线传输系统更加稳定,可靠性更高,我们提出了在软件和硬件方面提高可靠性的思路和方法,尤其是对软件方面的方法进行了重点的研究和探讨.     

故障树分析法及其应用

介绍了故障树分析法的基本原理及其应用实例，并利用c语言来解决可靠性问题。从实验中，获得了值得借鉴的经验。     

Comparison of in-situ measurement techniques of solder joint reliability under thermo-mechanical stresses

Thermo Mechanical Cycle Lifetime (TMCL) test is a widely used test methodology for evaluating the reliability of solder joints in the microelectronics industry. The commonly used measurement techniques to monitor solder joint failures during the TMCL test are either event detector or data logger. In this study, TMCL test has been carried out on the same devices in parallel with both measurement techniques. The pros and cons of both techniques are compared. It is observed that the solder joint reliability results on the investigated samples by both techniques are comparable. The event detector can catch short intermittent events, while the data logger is able to capture the details of the solder joint degradation process. In applications for which performance is dependent on the transmission of signals with a frequency of several hundred megahertz or more, the event detector technique shall be used. In such cases the data logger technique may overestimate product lifetime. On the other hand, for some applications where the performance is less susceptible to intermittent solder joint interconnect interruption but more to the increase of the solder joint resistance, the data logger shall be used. In such cases the event detector technique may underestimate product lifetime. In conclusion depending on the end application of the device, the most suitable technique can be selected.     

几种发射分集OFDM系统信道估计方法性能评估

给出了3种基于发射分集的OFDM系统信道估计方法,分别从训练序列对算法的影响、估计准确度、算法复杂度和算法适用性等方面对各自性能作了分析比较,并进行了仿真.分析比较和仿真结果表明,训练序列对3种算法的影响很大,通过训练序列的正交化设计,LS和EM算法可以得到很大程度的简化;EM算法与LS算法估计精度相当,信噪比较大时,多项式模型算法估计精度要远远高于LS和EM算法;总体上来说,多项式模型算法复杂度最高,EM算法复杂度最低.     

计算无圈有向网络ST可靠性的一个新方法

本文考虑计算无圈有向网络的ＳＴ可靠性问题（至少存在一条从源点ｓ到汇点ｔ的正常运行道路的概率）。文章引进了深度优先搜索（Ｄｅｐｔｈ－ＦｉｒｓｔＳｅａｒｃｈ）有序根树的概念并提出一个新的计算无圈有向网络ＳＴ可靠性的拓扑公式。以该公式为基础,我们利用ＤＦＳ方法提出一个新的计算无圈有向网络ＳＴ可靠性算法,它能生成简洁的可靠性表达式,进而有效地计算无圈有向网络的ＳＴ可靠性。两个例子例证了我们的结论