焊点热疲劳失效原因分析

某PCBA样品在使用约半年后出现功能失效,该PCBA在封装后进行整体灌胶,将失效样品剥离,发现部分器件直接脱落,通过表面观察、切片分析、EBSD分析、应力分析、热膨胀系数测试等手段对样品进行分析,结果表明:各封装材料存在热失配,且焊点缺陷较多且存在应力集中区,加速焊点的疲劳失效进程,导致PCBA功能失效。     

PBGA焊点开路失效原因分析及工艺改进措施

由于PBGA组件的焊点位于器件与PCB之间,焊点的检查和返修成本较高。控制PBGA组件焊点开路失效显得尤为重要。本文通过几个典型案例,总结分析了PBGA焊点开路的几种主要的失效原因,即:焊接浸润不良,PCB和PBGA的热稳定性差以及焊盘印刷焊膏量不足。对其失效机理进行了深入分析;在基础上,提出了工艺改进措施。     

基于子模型的电子封装焊点寿命预测方法研究

在向无铅化过渡的过程中,封装材料与工艺改变所带来的最突出的问题之一就是无铅焊点的可靠性问题。由于焊点区非协调变形导致的热疲劳失效是电子封装焊点的主要失效形式。到目前为止,仍无公认的焊点寿命和可靠性的评价方法。本文采用统一型粘塑性本构模型描述SnAgCu焊点的变形行为,在对焊点可靠性分析的基础上采用基于能量的寿命模型进行焊点寿命预测;在有限元方面采用子模型的处理技术,并采用节点平均化以及体积平均化方法计算寿命模型相关参数。力图从理论方面和有限元处理技术方面改进以达到提高焊点寿命预测效率及预测精度的目的。     

塑封SIP集成模块封装可靠性分析

塑封器件具有体积小、成本低的优点,逐步替代气密性封装器件,广泛地应用于我国军用产品中。军用塑封SIP(System In Package)产品集成度高、结构复杂、可靠性要求高等特点,对塑封工艺带来了挑战,目前国内工业级塑封产品不能完全满足军用可靠性要求,工业级塑封产品常在严酷的环境应力试验下表现出失效。本文针对工业级塑封SIP器件在可靠性试验过程中出现的失效现象进行分析研究,通过超声检测、芯片切面分析等手段,结合产品应力试验结果,分析导致塑封产品失效的关键原因,并针对失效机理提出优化改进方案。     

过应力试验改善TSPC603RMG8LC芯片CBGA焊点疲劳失效中的应用

CBGA(Ceramic welding ball array package)芯片焊点疲劳失效情况是电子产品经常出现的一种故障现象。如何改善并验证CBGA芯片焊点疲劳失效工艺的有效性是目前仍没有完整的较好的方法。本文介绍了基于不同工艺的试验样品,通过对CBGA芯片焊点不同工艺情况进行过应力加速温度循环试验情况,实现了CBGA芯片焊点疲劳失效改善工艺的验证试验,提出了过应力加速试验是验证工艺改善的可行性的有效途径。     

QFP封装焊点随机振动分析与优化

随着电子产品与系统的日益复杂化,利用仿真的手段来解决产品尚处在研发阶段的可靠性问题已成为产品可靠性设计的重要一环.来源于实际的含QFP封装器件的工程案例单板,对QFP封装的引脚和焊点进行详细建模,利用ANSYS Workbench对QFP封装焊点进行了随机振动分析,确定焊点的应力分布及危险焊点所在位置.根据随机振动仿真...     

光电耦合器失效模式与机理分析

本文通过典型失效案例介绍,结合光耦器件结构及工艺制程的特点,分析了器件本身缺陷引起光耦失效的机理。另一方面,结合光耦应用电路的特点,对外部电应力引起光耦失效的原因也进行了详细阐述。     

元器件在冲击环境下的可靠性——试验、仿真与理论模型

据统计,武器型号在研制生产过程由元器件失效引发的质量问题时有发生。而大量元器件的使用失效由冲击环境造成,冲击对元器件的危害往往是致命的,引脚断裂,焊点脱落,器件腔体出现形变等等。因此型号在设计阶段必须考虑产品的冲击可靠性,比如产品级的冲击防护,类似保护箱,阻尼装置,吸能装置等,但这些产品级的防护不能完全保护元器件的可靠性。而近年来,电子元器件也朝着大规模,高集成化,小型化发展,新工艺,新材料也在不断应用,因此元器件在冲击环境下的可靠性保障工作也变得越来越有挑战性。     

电子设备热循环加速可靠性试验研究与应用

本文分析了电子设备热循环失效机理,介绍焊点热循环失效的Engelmaier-Wild寿命模型.应用Engelmaier-Wild寿命模型,本文提出了一种电子设备热循环加速可靠性试验方案.通过某电路板热循环加速可靠性试验案例及其试验数据,验证了Engelmaier-Wild寿命模型应用在电子设备热循环加速可靠性试验的适用...     

半导体器件键合失效模式及机理分析

本文通过对典型案例的介绍,分析了键合工艺不当,以及器件封装因素对器件键合失效造成的影响。通过对键合工艺参数以及封装环境因素影响的分析,以及对各种失效模式总结,阐述了键合工艺不当及封装不良,造成键合本质失效的机理;并提出了控制有缺陷器件装机使用的措施。     

Methods of Compliance Evaluation for Ocean Outfall Design and Analysis

Sewage discharge from an ocean outfall is subject to water quality standards, which are often stated in probabilistic terms. Monte Carlo simulation (MCS) has been used in the past to evaluate the ability of a designed outfall to meet water quality standards or compliance guidelines associated with sewage discharges. In this study, simpler and less computer-intensive probabilistic methods are considered. The probabilistic methods evaluated are the popular mean first-order second-moment (MFOSM) and the advance first-order second-moment (AFOSM) methods. Available data from the Spaniard's Bay Outfall located on the east coast of Newfoundland, Canada, were used as inputs for a case study. Both methods were compared with results given by MCS. It was found that AFOSM gave a good approximation of the failure probability for total coliform concentration at points remote from the outfall. However, MFOSM was found to be better when considering only the initial dilutions between the discharge point and the surface. Reasons for the different results may be the difference in complexity of the performance function in both cases. This study does not recommend the use of AFOSM for failure analysis in ocean outfall design and analysis because the analysis requires computational efforts similar to MCS. With the advancement of computer technology, simulation techniques, available software, and its flexibility in handling complex situations, MCS is still the best choice for failure analysis of ocean outfalls when data or estimates on the parameters involved are available or can be assumed.     

焊接工艺不当导致元器件失效的原因分析

通过对典型案例的介绍,分析了焊接工艺不当对元器件失效产生的影响。通过对焊接工艺过程中各种影响因素的分析,以及对各种失效模式总结,阐述了焊接工艺不当（包括焊接前,元器件的预处理不当）,造成元器件失效的失效原因与机理,在此基础上,提出了有针对性的改进措施。     

机载电子元器件环境应力筛选初探

讨论了某直升机机载电子元器件在环境应力筛选过程中存在的主要问题及其解决方法。包括环境应力筛选的实施原则,筛选项目的确定,失效元器件分析情况及失效元器件的处理等问题。     

LED失效分析手段研究

介绍LED产品常见的失效分析手段,主要包含外观检查、电性能测试、X-Ray透视检查、开封检查、金相切片分析、扫描电镜和能谱分析等手段,并结合实际案例对几种方法进行描述。     

失效机理在可靠性工程中的应用

可靠性工程技术中的众多工作项目需要建立在失效机理的基础上。了解和应用失效机理是改进产品可靠性的核心工作之一,在产品可靠性工程中被广泛应用。本文澄清了相关的基本概念,并且分析了失效机理在产品可靠性预计、寿命评估、故障模式及失效机理分析、可靠性试验以及失效分析方面的应用。     

湿热环境应力下产品失效机理分析

阐述了湿热环境下产品的失效模式,分析了在湿热环境应力下产品功能失效的原因,指出了产品一般都会受到湿度与温度的综合影响,产品的各种劣化效应往往是产品表面受潮和体积受潮两种现象所造成的,并针对性地提出了对产品进行有效防护的方法.     

某输出缓冲器的失效分析

本文通过对某输出缓冲器在质量一致性检验中的ESD考核环节失效的情况进行分析,找到了产品测试系统的异常情况,通过此次分析,进一步发现该产品的ESD保护设计一直以来存在的问题。文中不仅给出了失效机理,同时提出了改进措施并加以验证。此次失效分析对于同类器件的ESD保护设计,提高其可靠性具有一定的借鉴意义。     

印制电路板组件“三防”试验失效分析与案例

通过"三防"试验分析与案例,提高三防设计或工艺的科学性、合理性。本文阐述了湿热、盐雾、霉菌试验失效主要原因与案例,本文阐述了影响聚对二甲苯气相沉积涂敷,镀覆,液态涂料涂敷,应力筛选,密封等试验失效因素,从试验方法、工艺控制、材抖选择等诸多方面进行分析,探讨"避免"失效的措施。     

PLANNING METHODOLOGY FOR ANALYSIS AND MANAGEMENT ON LAKE EUTROPHICATION1

ABSTRACT: The effects of changing nutrient inputs through land use management, waste water treatment, or effluent diversion are not clear, and managers are discovering that decisions which were effective in reversing eutrophication for one lake are often unsuccessful when applied to another. Simple empirical relationships are often used to predict the impact of management decisions. Errors in estimation could result in either substantial costs for overdesign or failure to meet desired eutrophication levels. This paper presents and illustrates a methodology to evaluate the impact of land use and water resource management decisions on lake eutrophication. The problems of worth of additional information, and uncertainty of estimates were handled within a cost-effectiveness framework. The probability of exceeding a critical level of eutrophication was considered as a measure of effectiveness. The cost criterion is the expected value of opportunity costs, costs of analysis and costs of additional information. Uncertainty analysis techniques were used to estimate the effectiveness of various management alternatives. Bayesian methods can be utilized to determine the worth of additional information. The methodology was applied to Beseck Lake, Connecticut, and the cost and effectiveness measures estimated for a number of land management alternatives. Worth of additional information was not determined in this initial effort in uncertainty analysis for lake eutrophication management.     

Environmental pollution,hydropower and nuclear energy generation before and after catastrophe: Bathtub-Weibull curve and MS-VECM methods

In this paper, the life span of hydro and nuclear energy generations and the relationship between hydro and nuclear energy generations, environmental pollution, and economic growth were investigated for Japan covering the period of 1960–2018 by employing the Bathtub-Weibull curve and Markov switching-vector error correcting (MSVEC) method, respectively. According to the Bathtub-Weibull curve analysis, a rising failure rate for nuclear energy was found, indicating that the life of nuclear energy has expired, but a decreasing failure rate for hydroelectric energy has been detected. Then two different MSVEC models were used. The MSVEC method, unlike traditional approaches, determines the relationship between variables under different regimes. The results of MSVEC methods indicate three important points. First, regime-dependent asymmetry and regime changes are crucial for policy recommendations. Second, the shocks to hydropower and nuclear energy generations cause temporary deviations from the long-run growth path in both regimes. Lastly, the increase in hydropower generation leads to a decrease in environmental pollution and an increase in GDP, and an increase in nuclear power generation increases pollution and growth in both regimes.