Reliability of SiGe HBTs for Power Amplifiers—Part II: Underlying Physics and Damage Modeling

This paper presents the underlying physics and modeling of aggressively biased cascode SiGe heterojunction bipolar transistor power amplifier (PA) cores under large-signal operating conditions. The damage characteristics observed during RF operation, particularly the base leakage and collector-base (CB) junction failure, are investigated in detail using dc stress methods. Base leakage was characterized across geometry, voltage, and current conditions, and a damage model is purposed based on Shockley–Read–Hall theory and the reaction–diffusion equation. This model is used to predict damage under aggressive RF operations, in order to extract the operational lifetime of SiGe PAs. The onset of CB junction failure was modeled using the current-gain collapse model, and it accurately captures the failure threshold current $I_{rm Fail}$ observed during RF stress.      

熔断器的可靠性评估

本文把一般可靠性技术应用于熔断器领域,根据熔断器的职能、工作特性,提出了熔断器可靠性的数量指标、评估方法,并探讨了熔断器理论的另一个重要分支——熔断器的可靠性理论。     

接地装置连接用放热焊粉研制及接头性能研究

放热焊接在接地系统施工中得到了广泛应用,为建设既安全又经济的接地网,研制出性价比高的焊粉是关键.研制了接地工程用放热焊粉,进行了导电率、抗拉强度等性能试验,并与进口放热焊粉、国产某煤粉进行对比.结果表明:自研放热焊粉与进口产品性能相当,且性价比更高.最后,确定了评价焊接接头性能的技术指标.     

焊接接头疲劳强度和寿命估算

根据等效能量密度理论计算焊趾的循环应力 ,结合材料的 S- N曲线 ,估算焊接接头疲劳强度或疲劳寿命 ,并通过 15Mn VN钢焊接接头进行拉伸疲劳试验 ,验证本方法的有效性。试验结果表明 ,本方法可应用于焊接结构的疲劳性能分析     

适用于配电网规划的可靠性指标改进显式估算算法

针对计及可靠性的配电网规划问题,提出一种可靠性指标的改进显式估算算法。以树编辑距离作为馈线拓扑结构间的差异性计量,对待评估区域内的配电馈线按拓扑结构层次聚类。将聚类中心作为区域典型拓扑,以它们取代传统估算方法中的简单辐射状结构,建立可靠性估算模型。模型基于各类拓扑结构的故障隔离能力与负荷转供能力,通过回归分析推导可靠性指标显式计算公式,并分析了不同停电方式与多种可靠性提升设备产生的影响。一个实际城市配电网的算例分析表明,算法在面对多样化网架结构时亦能保证较高的计算精度,且有助于提升配电网规划模型的求解质量与求解稳定性。     

Interaction Effect of Voids and Standoff Height on Thermomechanical Durability of BGA Solder Joints

This paper documents simulation studies on the interactive effect of standoff height and void volume on the thermomechanical durability of ball-grid-array solder joints using a 3-D viscoplastic finite element analysis. Surface Evolver software was used to find the optimized shape of the solder joints and standoff height by minimizing the surface energy as voids with different sizes were placed in solder balls. A global–local modeling approach was then utilized to model the thermomechanical durability of voided solder joints. Void-area-fraction ranges of 14%–40% were analyzed. A nonmonotonic behavior of durability versus void area fraction was observed. The results showed that, if the void is completely inside the solder ball and has no interface with the boundaries of the joint, it does not have a detrimental effect and even improves the durability as the void size increases. However, voids located at the interface of the solder joint and copper pads were found very detrimental to durability. Factors such as load bearing area, stress concentration factor, and overall compliance of the structure were found responsible for the nonmonotonic behavior of the joints. An analytical micromechanics approach was used to calculate the compliance of the structure, and a nonmonotonic trend in phase with the durability trend was observed. The stress concentration factor also showed the same nonmonotonic trend. The rise of these two factors for the void interfacing with copper pads in addition to the decreased-load-bearing-area effect resulted in a drastic decrease in durability.      

含分布式电源的配电网可靠性评估综述

介绍了分布式发电的概念和特点,概述了国内外分布式发电技术的研究现状,并分析了分布式电源的接入对配电网可靠性评估的影响。指出分布式电源的接入改变传统配电网的辐射状的结构,使潮流双向流动,孤岛运行和分布式电源输出功率的不确定性给配电网的可靠性评估带来新的挑战,并从分布式电源的可靠性评估模型、分布式电源的孤岛划分、负荷及元件可靠性参数的不确定性对含分布式电源的的新型配电网可靠性评估进行了阐述。最后提出含分布式电源的新型配电网可靠性评估中急需攻破的几个难题。     

早期产品可靠性预计存在的问题及对策

针对早期产品在可靠性预计过程中存在的普遍问题,以具有代表性的产品为例,给出了相应的对策.     

Simple Time-to-Failure Estimation Techniques for Reliability and Maintenance of Equipment

In 1979, MIT produced a report on maintenance with a focus on tribology. They estimated that $200 billion US dollars were spent on the direct costs associated with reliability and maintenance (R&M) [1]. At the time it was also estimated that over 14% of the 1979 gross domestic product (GDP) was lost opportunity due to improper R&M practices [2]. This level continued to increase as the industrial infrastructure aged, as well as other reliability-based reasons, to over 20% of the US GDP, or over $2.5 trillion in lost business opportunity [3]. This is greater than all but the top three economies in the world! At this time it is estimated that the R&M industry is approximately $1.2 trillion in size with up to $750 billion being the direct cost of breakdown maintenance (reactive) or generally poor, incorrect or excessive practices [4].The primary cause of the loss is that over 60% of maintenance programs are reactive, and the number is growing [2], which includes those programs which were initiated and later failed due to "maintenance entropy," or collapsing successful programs where the significant paybacks are no longer seen. At this time over 90% of maintenance initiatives fail, 57% of computerized maintenance management system (CMMS) applications fail, and over 93% of motor management programs fail [4]. The primary reason is that the present business mindset calls for immediate improvements, whereas it normally takes 12 to 24 months for a supported program to take hold and begin to show results?a rule of thumb that applies to all business practices.     

风电场可靠性建模

考虑风速和风向的随机变化、风电机组的功率特性、不同风电场之间风速的相关性以及风电机组停运模型、风电场尾流效应和气温的影响,建立了风电场可靠性模型及尾流效应模型。仿真结果验证了所提模型的有效性。该模型为进一步研究含风电场的电力系统可靠性评估、风电场容量可信度以及其他风电场并网问题打下了基础。     

高速铁路牵引供电系统的供电可靠性评估方法

提出了高速铁路牵引供电系统可靠性评估的5个层次,针对层次1进行可靠性评估,在考虑越区供电的前提下定义了高速铁路牵引供电系统的可靠性指标,推导了用元件可靠性参数表示的供电可靠性指标的解析表达式和灵敏度表达式。以RBTS系统对某高速铁路供电为例,通过可靠性计算和灵敏度分析确定了影响高速铁路牵引供电系统的供电可靠性和铁路通过能力的薄弱环节。仿真结果表明该评估方法极大地提高了高速铁路牵引供电系统可靠性评估的计算速度,避免了“维数灾”,得到的供电可靠性指标可直接作为牵引供电系统组合可靠性评估的理论依据。     

基于脉冲神经网络伪量测建模的配电网三相状态估计

为了给配电网管理系统提供全面准确的实时数据,配电网三相状态估计显得尤为重要。针对当前配电网量测信息不足,提出了基于脉冲神经网络(SNN)伪量测建模的配电网三相状态估计。该方法首先将实时和部分历史支路功率量测输入SNN进行伪量测建模,然后由高斯混合模型生成相应的量测误差,最后进行基于加权最小二乘法的配电网三相状态估计。理论分析和算例验证表明,所提模型不仅能够在正常通信时有效提高配电网状态估计精度,而且能在通信故障时保证估计精度在合理范围内,进而为配电网的运行控制提供参考依据。     

含有统一接口的微电网系统可靠性建模研究

采用统一接口系统的微电网可靠性问题较为特殊,需要单独建模。结合概率统计思想,将稳定性问题分为软件问题和硬件问题两大类,并提出了平均失效时间和最短失效时间的计算依据,根据电网结构的并联和串联规律进行有效失效时间的计算,进而评估整个微电网系统的可靠性,得出了基于概率统计和网络结构的针对微电网的可靠性建模方法。最终通过IEEE34节点测试系统进行计算,说明了该方法的计算流程。     

分类用户单位停电损失函数的确定及应用

分类用户单位停电损失函数(SCUDF)对配网可靠性措施效益评估、电力系统规划等预测性研究具有重要意义。单纯采用用户问卷调查法虽然较为准确,但由于资金和时间的限制仍有很大的难度,且因地区生产结构及自动化水平的差异而难以从其他地区的已有数据类比取得。提出一种根据分类用户用电量及其相应生产总值的若干年统计数据,运用回归分析及参数估计原理得出SCUDF的方法。该方法避免了大量的统计工作,其数据可直接从相关权威部门获取。文中估算了广州某地区配网的SCUDF,据此计算了一条现有馈线的当前可靠性水平下的停电损失,表明该方法可行。     

基于MIL-HDBK-217F模型微机保护装置可靠性预计

介绍了微机保护装置的两个基本的可靠性预计指标,即误动失效率和拒动失效率,进一步丰富了微机保护装置可靠性的评价指标体系;应用基于MIL-HDBK-217F模型的可靠性预计方法建立了微机保护装置可靠性预计模型,并结合算例验证了模型的正确性.     

配电网信息物理系统可靠性的精细化建模与评估

随着信息通信技术广泛应用于配电网,配电网的信息物理耦合程度逐渐加深,现有配电网信息物理系统可靠性模型难以准确评估实际工程应用中复杂场景的可靠性.文中基于耦合元件的失效情况建立了多状态可靠性模型,并基于满二叉树拓扑遍历配电网信息失效场景,由此提出了一种新颖的可靠性分析方法.该方法考虑了实际故障处理过程与转供容量约束,并适...     

风力发电机组可靠性建模与维修策略优化

风力发电的快速发展使得风电机组结构越来越复杂,故障率也随之提高.为了提高风力发电机组的可靠性,提出了一种风力发电机组的可靠性优化策略.以双馈风力发电机为例,运用马尔可夫过程数学模型和可靠性理论建立风力发电机组的可靠性模型,在此基础上构造风电机组老化、故障和维修的网络结构图,从而得到风电机组可靠性最优时的维修策略.     

Compact Modeling and Simulation of Circuit Reliability for 65-nm CMOS Technology

Negative bias temperature instability (NBTI) and channel hot carrier (CHC) are the leading reliability concerns for nanoscale transistors. The de facto modeling method to analyze CHC is based on substrate current I_sub, which becomes increasingly problematic with technology scaling as various leakage components dominate I_sub. In this paper, we present a unified approach that directly predicts the change of key transistor parameters under various process and design conditions for both NBTI and CHC effects. Using the general reaction-diffusion model and the concept of surface potential, the proposed method continuously captures the performance degradation across subthreshold and strong inversion regions. Models are comprehensively verified with an industrial 65-nm technology. By benchmarking the prediction of circuit performance degradation with the measured ring oscillator data and simulations of an amplifier, we demonstrate that the proposed method very well predicts the degradation. For 65-nm technology, NBTI is the dominant reliability concern, and the impact of CHC on circuit performance is relatively small.     

电动机寿命分布分析和可靠性估计

针对图估法和假设检验法的不足,用线性回归分析方法研究了电动机的寿命分布类型,并用最小二乘法计算了分布函数的未知参数。本文以起重电动机作为计算实例,结果表明该电动机的寿命服从三参数威布尔分布,给出了电动机的累积分布函数,可靠度曲线和有关关可靠性等特征量。