A comparison of electronic-reliability prediction models

One of the most controversial procedures in reliability is the use of reliability prediction techniques based on component failure data to estimate system failure rates. The International Electronics Reliability Institute (IERI) at Loughborough University is in a unique position. Over many years, much reliability information has been collected from leading British and Danish electronic manufacturing companies. These data are of such high quality that IERI can perform the comparison exercise with many circuit boards (CB) of different types. Several CB were selected from the IERI field-failure database and their reliability was predicted and compared with the observed field-performance. The prediction techniques were based on the: M217E [US Mil-Hdbk-217E]; HRD4; Siemens (SN29500); CNET; and Bellcore (TR-TSY-000332) models. For each model, the associated published failure rates were used. Hence, parts count analyses were performed on several CB from the database; these analyses were compared with the field failure rate. The prediction values differ greatly from the observed field behavior and from each other. Further analysis showed that each prediction model was sensitive to widely different physical parameters. The results are summarized. Some of the models are more sensitive to a factor that varies according to an Arrhenius model, such as temperature and electrical stress, while others are more sensitive to the discrete π factors used to model environment and quality     

A Comparison of Several Component-Testing Plans For A Parallel System

We consider a parallel (1-out-of-n:G) system of n components with constant failure rates and treat three different classes of component testing procedures all of which guarantee that the given consumer and producer risks are not exceeded. It is necessary to impose certain restrictions on the magnitude of the unknown failure rates for guaranteeing the producer risk. The three classes of component test procedures use Type-I censoring and use decision rules based on: A) the total number of component failures during the testing periods, B) the number of failures for each individual component, and C) the maximum likelihood estimate of system reliability. Based on the requirement that both the consumer and producer risks lie within specified levels, class A plans exhibit lower testing costs in the selected numerical examples.     

Plastic encapsulated microcircuit reliability predicition: why?

Reliability prediction models for microcircuits have been a function of steady-state temperature. Failure rates generated from accelerated temperature tests were extrapolated to predict system reliability at system use temperatures. This is now known to be completely inaccurate. Attempts are now being made to predict the reliability of plastic encapsulated microcircuits (PEMs) based on accelerated temperature/humidity testing. Failure rates generated due to corrosion failure mechanisms at these high stress levels are then extrapolated and used to predict system reliability at used temperature/humidity conditions.This paper discusses the fallacy of this approach. A new concept for the assurance of PEM corrosion resistance is proposed. It will be shown that today's best commercial practice suppliers have already addressed the design, materials, and processing issues of molded packaged microcircuits, and corrosion is no longer a mechanism of concern to the user.     

C4ISR系统可靠性评价方法与技术研究

分析了国内外C^4ISR系统可靠性研究现状以及可靠性评价的研究方向，初步建立了评价的指标体系，并对相关方法与技术进行了归纳总结。针对评价不同的指标可能采用不同的方法与技术组合的现实，进行了基于逻辑框图的C^2分系统任务可靠度评价研究，然后引入时延这一反映C^4ISR系统可靠性的性能指标，并通过建立对象Petri网模型对时延的定量评价进行了研究。评价实例初步体现了方法的可行性。     

Reliability Evaluation and Prediction for Discrete Semiconductors

The use of accelerated step-stress and constant stress-in-time test techniques is demonstrated for generating models for predicting reliability at use conditions. Reliability prediction models were obtained for a signal diode, signal and power transistors, silicon trolled rectifier, and metal oxide varistor. Each of these device types follows the Arrhenius model for reliability prediction. Techniques are demonstrated for determining 1) the acceleration factor between extremely high acceleration testing conditions and field operating conditions on the signal diode; and 2) the acceleration or multiplying factor between high level stresses and use conditions which can be used to predict the performance of the signal diode over time. The effect of relative humidity on reliability is discussed. Devices under power operation have a lower relative humidity (RH) than the environment. This low RH suppresses humidity activated mechanisms. A transistor high-reliability screen which removes devices with early manufacturing type defects is described. This screen was effective, efficient and economical for improving the reliability of systems. A technique of combining acceleration factors for a number of items which affect reliability was demonstrated for the diode. This same technique should be useful for most device reliability predictions. The acceleration factors, however, can not be extrapolated into stress levels much above maximum ratings where new failure modes may appear that override the established failure rate relation with stress. The straight line plots of failure rates in this paper are terminated before these threshold limits.     

A Method for Predicting VLSI-Device Reliability Using Series Models for Failure Mechanisms

A series model is used to determine the intrinsic reliability of an integrated circuit. An analysis of electromigration in the interconnect system of a 200 000 transistor VLSI device, shows that the failure rate exceeds 10 FIT (failures per 109 hours) within 2 years when operating at a temperature of 800 C. These results indicate the importance of fundamental wear-out mechanisms as factors in VLSI device reliability, under usual operating conditions. The analysis, as applied to a generic chip, predicts that temperature, burn-in, and complexity all adversely affect the device reliability. The paper demonstrates the feasibility of using the information available in the design database together with specific failure models to predict (during the design phase) the reliability of an IC. These techniques can be used to develop a CAD tool for reliability prediction.     

A Best Practice Guide to Resource Forecasting for Computing Systems

Recently, measurement-based studies of software systems have proliferated, reflecting an increasingly empirical focus on system availability, reliability, aging, and fault tolerance. However, it is a nontrivial, error-prone, arduous, and time-consuming task even for experienced system administrators, and statistical analysts to know what a reasonable set of steps should include to model, and successfully predict performance variables, or system failures of a complex software system. Reported results are fragmented, and focus on applying statistical regression techniques to monitored numerical system data. In this paper, we propose a best practice guide for building empirical models based on our experience with forecasting Apache web server performance variables, and forecasting call availability of a real-world telecommunication system. To substantiate the presented guide, and to demonstrate our approach in a step by step manner, we model, and predict the response time, and the amount of free physical memory of an Apache web server system, as well as the call availability of an industrial telecommunication system. Additionally, we present concrete results for a) variable selection where we cross benchmark three procedures, b) empirical model building where we cross benchmark four techniques, and c) sensitivity analysis. This best practice guide intends to assist in configuring modeling approaches systematically for best estimation, and prediction results.     

A survey of reliability-prediction procedures for microelectronicdevices

The author reviews six current reliability prediction procedures for microelectronic devices. The device models are described and the parameters and parameter values used to calculate device failure rates are examined. The procedures are illustrated by using them to calculate the predicted failure rate for a 64 K DRAM; the resulting failure rates are compared under a variety of assumptions. The models used in the procedures are similar in form, but they give very different predicted failure rates under similar operating and environmental conditions, and they show different sensitivities to changes in conditions affecting the failure rates     

A New Sample-Based Approach to Predict System Performance Reliability

Multiple degradation paths arise when systems operate under uncontrolled, uncertain environmental conditions at customers' hands in the field. This paper presents a design stage method for assessing performance reliability of systems with competing time-variant responses due to components with uncertain degradation rates. Herein, system performance measures (e.g. selected responses) are related to their critical levels by time dependent limit-state functions. System failure is defined as the non-conformance of any response, and hence unions of the multiple failure regions are formed. For discrete time, set theory establishes the minimum union size needed to identify a true incremental failure region that emerges from a safe region. A cumulative failure distribution function is built by summing incremental failure probabilities. A practical implementation of the theory is manifest through evaluating probabilities by Monte Carlo simulation. Error analysis suggests ways to predict and minimize errors. An electrical temperature controller shows the details of the method, and the potential of the approach. It is shown that the proposed method provides a more realistic way to predict performance reliability than either worst-case, or simple average-based approaches that are available in the open literature.     

电子元器件与系统可靠性保障的PHM新方法

电子元器件与系统是各种设备和系统中不可或缺的部分,其可靠性是整机系统可靠性的决定性因素。为实现系统状态的实时监控,提供失效预警,避免灾难性故障的发生,阐述了故障预兆与健全管理（PHM）用于电子元器件与系统可靠性预测的原理与方法,详细分析了预兆单元法、失效征兆监控法和寿命损耗检测法可行性。     

Mission Reliability for a 1-Unit System with Allowed Down-Time

This paper considers a 1-unit system; the unit is repaired upon failure. The failure and repair rates need not be constant. The system fails if the unit is not repaired within a fixed time, or if the number of failures during the mission exceeds a fixed number. As a special case, that number is allowed to be ``infinite.' The Laplace transforms of the reliability and mean time to system failure are derived; they are not easily solved. The special case of constant failure and repair rates is treated. The results are compared with those of Calabro.     

Progress in reliability research in the micro and nano region

Due to the rapid development of IC technology the traditional packaging concepts are making a transition into more complex system integration techniques in order to enable the constantly increasing demand for more functionality, performance and miniaturisation. These new concepts will have to combine smaller structures and layers made of new materials with even higher reliability. As these structures will more and more display nano-features, a coupled experimental and simulative approach has to account for this development to assure design for reliability in the future. A necessary “nano-reliability” approach as a scientific discipline has to encompass research on the properties and failure behaviour of materials and material interfaces under explicit consideration of their nano-structure and the effects hereby induced. It uses nano-analytical methods in simulation and experiment to consistently describe failure mechanisms on that length scale for more accurate and physically motivated lifetime prediction models for use on a larger (i.e. then the micro) scale. This paper deals with the thermo-mechanical reliability of microelectronic components and systems and methods to analyse and predict it. Various methods are presented to enable lifetime prediction on system, component and material level, the latter introducing the field of nano-reliability for nano-packaging in advanced electronics system integration.     

Computer-Oriented Formulation of Transition-Rate Matrices via Kronecker Algebra

This paper formulates the differential equations typical of a Markov problem in system-reliability theory in a systematic way in order to generate computer-oriented procedures. The coefficient matrix of these equations (the transition rate matrix) can be obtained for the whole system through algebraic operations on component transition-rate matrices. Such algebraic operations are performed according to the rules of Kronecker Algebra. We consider system reliability and availability with stress dependence and maintenance policies. Theorems are given for constructing the system matrix in four cases: * Reliability and availability with on-line multiple or single maintenance. * Reliability and availability with system-state dependent failure rates. * Reliabilityand availability with standby components. * Off-line maintainability. The results are expres § ed in algebraic terms and as a consequence their implementation by a computer program is straightforward. We also obtain information about the structure of the matrices involved. Such information can considerably improve computational efficiency of the computer codes because it allows introducing special ideas and techniques developed for large-system analysis such as sparsity, decomposition, and tearing.     

Estimation of system reliability using a "non-constant failurerate" model

One of the most controversial techniques in the field of reliability is reliability-prediction methods based on component constant-failure-rate data for the estimation of system failure rates. This paper investigates a new reliability-estimation method that does not depend upon constant failure rates. Many boards were selected from the Loughborough University field-reliability database, and their reliability was estimated using failure-intensity based methods and then compared with the actual failure intensity observed in the field. The predicted failure-intensity closely agrees with the observed value for the majority of a system operating lifetimes. The general failure intensity method lends itself very easily to system-reliability prediction. It appears to give an estimate of the system-reliability throughout the operating lifetime of the equipment and does not make assumptions, such as constant failure rate, which can be detrimental to the validity of the estimate. The predictions seem, on present evidence, to track the observed behavior well, given the uncertainties that are evident in the field. The failure intensity method should be investigated further to see if it is feasible to estimate the system reliability throughout its lifetime and hence provide a more realistic picture of the way in which electronic systems behave in the field     

Laboratory reliability demonstration test considerations

An automotive company's goal is to design and manufacture vehicles that meet the needs and expectations of its customers. Laboratory (lab) testing is a critical step in developing vehicle components or systems. It allows the design engineer to evaluate the design early in the product development process. Establishing a good lab-test minimum-life requirement (bogey) is an important task for the engineer in order to provide a reliable product. When applying the techniques in this paper to the automotive industry, the test procedures can be generalized to any situation for which the Weibull distribution (with known shape parameter) appropriately describes failure behavior, and for which accelerated lab-tests are being correlated with field-test data. This paper covers approaches for determining reliability-test target development, lab-test bogey conversion, and the quantity of test samples (and the test length) which must be tested to meet the reliability demonstration target requirement     

Computationally-efficient phased-mission reliability analysis forsystems with variable configurations

Several techniques and a software tool for reliability analyses that generally apply to fault-tolerant systems operating in phased-missions are given. Efficient models, using Markov chains without an explosion of the state space, are provided for missions consisting of multiple phases, during which the system configuration or success criteria can change. In different phases, the failure rates and the fault and error handling models can also change, and the duration of any phase can use deterministic or random models. An efficient reconfiguration procedure that is computationally more efficient than any existing technique is developed. The technique is demonstrated using a numerical example to show the effects of mission phases on the system reliability     

Redundant-system demonstrated-reliability approximation usingpiece-part failure rates

A method of obtaining the reliability of a redundant system when only the part force-of-mortality estimates (hazard rates) for electronic parts are available is presented. Part failures are reported without specifying whether the parts are configured in series or in parallel. The sum of all the part failure rates in the system, recorded from the turn-on date of the system up to the present time of monitoring, and the sum of the failure rates of all the parts in the system recorded up to a certain previous time after the system turn-on date are calculated. The system reliability for a certain critical mission time, with or without redundancy, is calculated at that previous time. The method is useful in field-equipment reliability monitoring because exact computation is impossible without knowing whether the failed parts are configured in series or in parallel. Generally, Monte Carlo simulation should be used only to verify the results calculated through an analytic method, if such a method is available and is neither time consuming nor cost prohibitive. A dimensionless reliability parameter is introduced     

Fuzzy repairable reliability based on fuzzy gert

Military equipment and weapon systems have become more advanced, precise and complex. Requirements of threat and readiness have been raised. Nowadays, the advance of weapon systems and their logistic support places the emphasis on the life cycle in the initial design. However, reliability analysis is the main work of logistic engineering. Its aim is to develop the best design for weapon systems operating in a special operation environment. Accordingly, there are many factors to consider in the reliability of weapon systems. Generally, those factors are of an uncertain nature. Traditionally, we use probability theory to treat the reliability of a weapon system. The probabilistic approach can only represent the randomness of a success or failure event, and requires complete data and predetermined conditions. Fuzzy sets theory can efficiently treat the above characteristics and shortcomings. Therefore we will propose a method and technology of fuzzy system reliability to solve the above problems.In this paper we first formulate the building membership functions of component reliability based on the α-cut method. Secondly, when the membership functions of the components are built, we can propose some fuzzy mathematic models for solving fuzzy system reliability. Different models and approaches have been studied and proposed in this research. In an unrepairable system, we have built two methods. In a repairable system, we will propose a fuzzy GERT (graphical evaluation and review technique) method to calculate the fuzzy reliability. For a simple and efficient computation, we have developed systematic and practical algorithms to calculate and analyze fuzzy system reliability. We have also presented an example of a military operation mission to demonstrate our proposed methods.     

Estimation of Mission Reliability from Multiple Independent Grouped Censored Samples

Aircraft or missiles are flown for missions of varying durations. Data are collected at the end of each mission which indicate the mission duration and whether the equipment failed. The data are considered as multiple s-independent grouped censored samples with failure times unknown. The underlying failure model considered is the 2-parameter Weibull distribution. Maximum likelihood estimates are derived. The exponential distribution is used for comparison. Monte Carlo simulations are used to compare s-efficiency of estimates for grouped data with estimates if failure times were known. The asymptotic variance-covariance matrix was computed for the sampling conditions studied and was used to obtain lower s-confidence bounds on the system reliability.     

无线基站系统可靠性新模型探讨

对分布式基站的可靠性模型进行了讨论,提出了一种新的可靠性模型,命名为梳状模型,并给出了该模型的等价计算方法。梳状模型解决了分布式基站的系统服务任务可靠性指标的计算问题。根据分布式系统的物理意义,从系统可靠度的角度,进行理论推导,得出了梳状模型系统失效率和模块失效率的数学表达式。通过应用梳状模型,对于分布式基站系统进行建模和可靠性指标的计算,取得了良好的效果。