一种新的电子元器件突然失效率估算方法

在电子元器件可靠性特性的基础上,引入负荷系数的概念;同时考虑多种负荷的作用,建立了电子元器件突然失效率的估算模型;通过该模型所得的元器件突然失效率数据对电子设备及系统可靠性的计算更具有实际意义。     

一种新型微带端射平面树形天线的自动设计

将一种新的优化算法—自然树生长竞争算法,用于天线优化,结合基于有限元方法（FEM）的电磁场数值仿真软件,实现天线的自动设计,并设计出的新型微带端射平面树形天线。在5.77GHz～5.93GHz频段内S11〈-10dB,辐射方向保持良好的端射特性,且在5.8GHz的端射增益为5.4dBi。根据仿真结果,制作一个原型天线并对其进行测试,测试结果与仿真结果吻合良好。     

高稳定的可扩展覆盖网多播算法

提出了一种高稳定的可扩展覆盖网多播（SOM-HS, scalable overlay multicast with high stability）算法。SOM-HS算法定义了节点稳定度因子以及链路权重,能保证高稳定的节点位于多播树骨干网中。在分层分簇构造过程中,SOM-HS算法限制节点出度,保证节点负载均衡。实验结论表明,与现有其他算法相比,在不同组规模下,使用SOM-HS算法时的最大多播延时都最小。     

多层板层压过程中的尺寸收缩分析

在多层板制造过程中,内层芯板的收缩极大地影响了产品的质量。本文通过对多层板制作过程中的尺寸变形的分析,指出导致内层芯板变形的主要因素为材料热胀系数不匹配。通过对半固化片状态变化过程的分析,建立了层压过程各个阶段的数学模型。通过解析计算,得到结构为铜面/半固化片/铜面的一种高Tg芯板纬向菲林补偿系数为1.24668,与实际实验中得到的补偿系数比较接近。     

基于极化二元阵雷达的空域虚拟极化滤波算法

极化滤波利用干扰信号和目标信号的极化状态差异,可有效抑制有源压制干扰,然而,现有极化雷达需要两路发射通道和接收通道,存在系统复杂、实现代价高等诸多困难。该文提出了一种新体制极化雷达模型极化二元阵雷达,该系统仅需一路发射通道和接收通道即可实现极化测量。基于极化二元阵天线的空域极化特性,建立了有源压制干扰、目标回波的接收信号模型,研究了抑制有源压制干扰的空域虚拟极化滤波算法,仿真实验结果表明:对于窄带噪声调频干扰,信干比(SIR)改善因子能达到20 dB以上。     

焊点疲劳寿命的量化评价方法及其影响因素

焊点蠕变疲劳是电子产品破坏中一种最主要的形式,对焊点疲劳寿命的量化评价是电子产品可靠性分析中的关键环节。总结了IPC标准中的焊点蠕变疲劳模型,然后利用实例说明了如何在实际使用中对焊点寿命进行分析和预计,最后重点讨论了模型中的6个相关参数对焊点疲劳寿命及参数设计优化所带来的影响。分析表明,当有、无引脚器件的焊点间距分别大于1.143 0与0.063 5 cm时,器件的疲劳寿命均随引脚间距变大而急剧减小;此外,热失配仍然是影响焊点疲劳寿命的主要因素。     

一种随机相位估计简化EM算法

期望最大化（EM）算法在处理随机相位估计时是一个NP-完全问题,目前主要采用梯度算法来对其求解。但该方法存在计算量大、不易稳定且对相邻时刻估计结果依赖严重等问题。基于随机相位模型EM算法的因子图表示,提出了一种简化EM算法,其思想是只针对当前时刻进行独立的EM迭代计算,然后通过相邻相位偏转之间的关系对结果进行修正。仿真实验说明,该方法在减小计算量的同时,提高了算法性能。     

Above 700 V superjunction MOSFETs fabricated by deep trench etching and epitaxial growth

Silicon superjunction power MOSFETs were fabricated with deep trench etching and epitaxial growth,based on the process platform of the Shanghai Hua Hong NEC Electronics Company Limited.The breakdown voltages of the fabricated superjunction MOSFETs are above 700 V and agree with the simulation.The dynamic characteristics,especially reverse diode characteristics,are equivalent or even superior to foreign counterparts.     

Intrinsic stability of an HBT based on a small signal equivalent circuit model

Intrinsic stability of the heterojunction bipolar transistor(HBT) was analyzed and discussed based on a small signal equivalent circuit model.The stability factor of the HBT device was derived based on a compact T-type small signal equivalent circuit model of the HBT.The effect of the mainly small signal model parameters of the HBT on the stability of the HBT was thoroughly examined.The discipline of parameter optimum to improve the intrinsic stability of the HBT was achieved.The theoretic analysis resul...     

Optimization of Selective Epitaxial Growth of Silicon in LPCVD

Selective epitaxial growth (SEG) of silicon has attracted considerable attention for its good electrical properties and advantages in building microstructures in high‐density devices. However, SEG problems, such as an unclear process window, selectivity loss, and nonuniformity have often made application difficult. In our study, we derived processing diagrams for SEG from thermodynamics on gas‐phase reactions so that we could predict the SEG process zone for low pressure chemical vapor deposition. In addition, with the help of both the concept of the effective supersaturation ratio and three kinds of E‐beam patterns, we evaluated and controlled selectivity loss and nonuniformity in SEG, which is affected by the loading effect. To optimize the SEG process, we propose two practical methods: One deals with cleaning the wafer, and the other involves inserting dummy active patterns into the wide insulator to prevent the silicon from nucleating.