Fuzzy thermal modeling for MCM placement

This paper introduces a fuzzy analytical model for the optimal component placement of the power dissipating chips on a multichip module substrate. Our methodology considers multiobjective component placement based on thermal reliability as well as routing length criteria. The objective of the coupled placement methodology is to enhance the performance and reliability of the multichip module system by obtaining an optimal cost during multichip module placement. Case studies of the coupled placement are presented. In addition, the thermal distribution of the coupled placement results is simulated using the finite element method.     

一种T/R组件可靠性增长对策与评估

针对一种T/R组件交付系统使用中出现的故障率高、可靠性低事件,利用可靠性增长理论,结合组件设计、加工、使用等特点,提出建立T/R组件失效故障树模型的方法。对各种故障形式的基本事件进行了研究分析,从改进设计、完善工艺、更改器件选型和加强过程质量控制等诸多方面提出了可靠性增长对策。并就可靠性增长模型、可靠性增长评估统计分析方法进行了探讨,为评估分析提供了参考依据。     

Reliability analysis of a container spreader

The concepts of system reliability are applied to optimum replacement policies for a container spreader subsystem. Actual failure data of the spreader components are analyzed; and the probability distributions of these failures are determined. Models for optimum replacement policies for the spreader components are presented.     

General Failure Model Applied to Preventive Maintenance Policies

The reliability behavior of systems is investigated if two types of failures can happen. Type 1 is removed by minimal repair, Type 2 by replacement. Reliability expressions are derived. The results are used for calculating the s-expected long-run cost rate for a generalized age replacement policy and repair limits.     

Photovoltaic module reliability model based on field degradation studies

Crystalline silicon photovoltaic (PV) modules are often stated as being the most reliable element in PV systems. This presumable high reliability is reflected by their long power warranty periods. In agreement with these long warranty times, PV modules have a very low total number of returns, the exceptions usually being the result of catastrophic failures. Up to now, failures resulting from degradation are not typically taken into consideration because of the difficulties in measuring the power of an individual module in a system. However, lasting recent years PV systems are changing from small isolated systems to large grid‐connected power stations. In this new scenario, customers will become more sensitive to power losses and the need for a reliability model based on degradation may become of utmost importance. In this paper, a PV module reliability model based on degradation studies is presented. The main analytical functions of reliability engineering are evaluated using this model and applied to a practical case, based on state‐of‐the‐art parameters of crystalline silicon PV technology. Relevant and defensible power warranties and other reliability data are obtained with this model based on measured degradation rates and time‐dependent power variability. In the derivation of the model some assumptions are made about the future behaviour of the products—i.e. linear degradation rates—although the approach can be used for other assumed functional profiles as well. The method documented in this paper explicitly shows manufacturers how to make reasonable and sensible warranty projections. Copyright © 2008 John Wiley & Sons, Ltd.     

Optimization Procedure for the Analysis of Coherent Structures

The determination of the reliability level at which to manufacture the components of a coherent structure so that the system reliability h(p) is at a certain level and the overall system cost is minimized is considered. The cost of utilizing component ci at reliability level pi, Ci(pi), is assumed to be a convex increasing function of pi with a continuous first derivative and Ci'(qi)>0 where qi is the lower bound on the reliability level for component ci. Since for most coherent structures the constraint set defines a nonconvex set, any mathematical programming procedure blindly applied to the program converges to a local optimum rather than a global optimum. However, in certain cases, the global optimum can be found for the series and parallel (SP) type of systems. The key to the solution is to optimize each module separately and then to substitute a component for each module where the cost function for the component is the value of the objective function for the module. As long as the cost function for each module maintains the convexity property with In R or In(1 - R) as the argument (R being the reliability of the module), the optimization procedure can continue and a global optimum found.     

Effect of System Processes on Error Repetition: A Probabilistic and Measurement Approach

This paper presents an approach to system reliability modeling where failures and errors are not statistically independent. The repetition of failures and errors until their causes are removed is affected by the system processes and degrades system reliability. Four types of failures are introduced: hardware transients, software and hardware design errors, and program faults. Probability of failure, mean time to failure, and system reliability depend on the type of failure. Actual measurements show that the most critical factor for system reliability is the time after occurrence of a failure when this failure can be repeated in every process that accesses a failed component. An example involving measurements collected in an IBM 4331 installation validates the model and shows its applications. The degradation of system reliability can be appreciable even for very short periods of time. This is why the conditional probability of repetition of failures is introduced. The reliability model allows prediction of system reliability based on the calculation of the mean time to failure. The comparison with the measurement results shows that the model with process dependent repetition of failures approximates system reliability with better accuracy than the model with the assumption of independent failures.     

联机检修的冗余结构使用可用度模型修正

现场故障更换对象由电子和机电元器件改变为电子和机电更换模块后,备件保障就成为联机检修冗余结构任务可靠度和使用可用度模型中必须包含的一个关键参数。但在传统的联机检修任务可靠度和现行的使用可用度模型中没有得到或没有完全得到应有的反映。对此,提出了修正模型。在使用可用度模型中还对同时检修的平均修复时间模型作出了改正。     

工控计算机双机镜像软件设计

双机热备是工控计算机运行可靠性、稳定性、持续性的有力保障。设计了一套双机镜像软件来实现工控计算机的热备,该软件由心跳检测模块和资源管理模块组成,心跳检测模块通过发送心跳信息来检测计算机故障并保持双机连接;资源管理模块实现主/从机切换,资源状态查询、接管等任务。最终通过双机镜像软件实现双机热备,避免了生产过程中因计算机系统故障带来的损失。该设计的优点是方案灵活,投资成本低,缺点是在一定程度上降低了系统效率。     

System Design Issues for Harsh Environment Electronics Employing Metal-Backed Laminate Substrates

Designing harsh environment electronics continue to increase in difficulty to a rapid increase in feature content while electronics packaging technologies are often providing less reliability. In addition, restricted under-the-hood airflow and integrated (mechatronic) designs are significantly increasing operating temperatures toward their maximum operating capability. To provide a cost effective design, automotive electronics designers are pursuing circuit board assemblies directly attached to a metal plate. For cost purposes, this metal plate can also be used as part of the module housing to provide protection, as well as thermal efficiency. Unfortunately, the metal backing can often further reduce component reliability due to increases in substrate coefficient of thermal expansion. The paper investigates the impact of metal attachment on component reliability as it investigates the use of several board attachment options. These analyses are compared to finite element modeling to further understand the causes of earlier failure. In addition, the impact of additional component encapsulants and conformal coatings are investigated. Because all attachment materials must meet a certain thermal performance (both initial design and long-term performance) the thermal efficiencies of these design options are investigated, as well as the delamination due to product life. Finally, failure analyses are presented and ensure that failures match expected characteristics.     

System reliability with common-cause hazard to obey an exponential power model

A model is proposed for the analysis of systems subject to common-cause failures that are not considered constant and assume that they obey an exponential power model. To represent common-cause failures, we use the Marshall, Olkin formulation of the multivariate exponential distribution. That is, the components are subject to failure by Poisson failure processes that govern simultaneous failure of a specific subset of the components. The method for calculating system reliability requires that a procedure exists for determining system reliability from component reliabilities under the statistically-independent component assumption. The paper includes examples to illustrate the method.     

高冗余光纤光栅传感网络的设计与实验研究

结合无源光学器件,提出并设计了一种新型的高冗余光纤布拉格光栅(FBG)传感模块,并将设计的FBG传感模块与波分复用技术相结合,构建了高冗余FBG传感网络.以长方形铝合金板为研究对象,对高冗余FBG传感网络的可靠性进行研究,理论比较并实验分析了高冗余FBG传感阵列的适用性与可靠性.研究结果表明,利用光开关在传感阵列支路之间的切换,使得FBG传感网络更具有冗余性.这一方面能够解决使用过程中多个部位出现故障导致的某些FBG传感模块无法被计算机检测到的问题,有效提高了传感系统的可靠性、容错性;另一方面为工程应用中结构健康监测以及特殊部位监测提供了一种有效可行的监测手段.     

Using a software reliability model to design a telecommunicationssoftware architecture

The author proposes a software reliability model for a large real-time telecommunications software architecture. Some simple examples of the critical components of the software architecture and their dependencies are described. The component dependencies permit the propagation of faults from the component in which the fault originates to the other components. This propagation can cause failures in the chain (or in the tree) of components. Detection and failures depends on the tests executed or on the number and type of customer requests. An error can occur in any component. This error can be caused by a fault that propagated from another component or it can be a fault that originates in that component. The error can be traced through the component-dependency chain (or tree) to repair all the faults that are associated with that error. The software reliability model guides the design of the software architecture     

Design of Dependent-Failure-Tolerant Microcomputer System Using Triple-Modular Redundancy

Microcomputer system reliability using triple-modular redundancy (TMR) is discussed when failures exist not only in any single module but also in any two or three modules at a time. The optimal time interval is calculated by which the system will even be resynchronized periodically so that additional transient failures can be tolerated. It is shown that in spite of the optimal reaynchronisation, the reliability of the system cannot be improved by the ordinary TMR under some dependent-failures. For the purpose of eliminating the effect of dependent-failures, a new fault-tolerant microcomputer system is proposed where a program is executed three times by three CPU's.     

Reliability evaluation of a first order standby system with module redundancy

By defining a module to be a coherent subsystem of independently operating components each with a constant failure rate, this article derives expressions for the reliability of a standby redundant system consisting of an operating module together with a cold or warm standby module. The closed form reliability expressions are dependent upon the minimal path sets of each module as well as the component failure rates. Expressions are also derived for the mean time to system failure as well as the variance of the system time to failure distribution.     

System Reliability in the Presence of Common-Cause Failures

This paper presents a method for calculating the reliability of a system depicted by a reliability block diagram, with identically distributed components, in the presence of common-cause failures. To represent common-cause failures, we use the Marshall & Olkin formulation of the multivariate exponential distribution. That is, the components are subject to failure by Poisson failure processes that govern simultaneous failure of a speciflc subset of the components. The method for calculating system relability requires that a procedure exist for determining system reliability from component reliabilities under the statistically-independent-component assumption. The paper includes several examples to illustrate the method and compares the reliability of a system with common-cause failures to a system with statistically-independent components. The examples clearly show that common-cause failure processes as modeled in this paper materially affect system reliability. However, inclusion of common-cause failure processes in the system analysis introduces the problem of estimating the rates of simultaneous failure for multiple components in addition to their individual failure rates.     

Reliability model for Al wire bonds subjected to heel crack failures

In power electronic packages wire bonding is used for the electrical contact of the chips and for interconnections on the module substrate. Limiting factors for the reliability are solder fatigue and wire bond failures. In this work we investigate the material fatigue of aluminum bonding wires stressed by cyclic lateral bonding area displacement. Bond wire heel crack failures observed by experiments are found to be strongly dependent on the loop geometry. Based on a finite element model that accounts for elastic-plastic material properties, a life-time model for the Al wire (Coffin-Manson representation) is derived from the experiments.     

Real-time furnace modeling and diagnostics

Precise control of process temperature has become increasingly important in today's semiconductor industry. Multizone batch furnaces are used widely in current manufacturing lines, and high reliability of furnace systems is a crucial factor in achieving high product yield. However, uncertainty caused by sensor noise and failure may degrade reliability. In this work, the authors develop a methodology based on thermal modeling and sensor fusion techniques to detect temperature sensor failures, power supply failures, and system faults for the multizone furnace systems. The typical types of failures have been defined. The impact of single failures and different combinations of failures on the system behavior has been studied. The furnace system has been modeled based on both physical considerations and experimental data extraction. The fault detection methodology has been tested in simulations. Principal component analysis is utilized for choosing data types for different fault detection purposes. Sensor fusion is used to enhance reliability. Simulation results show that all different types of failures can be detected when data are rich enough. Experimental results show that all single failures and some of the failure combinations can be estimated when only steady-state and cooling-down data are utilized.     

Periodic replacement when minimal repair costs depend on the age and the number of minimal repair for a multi-unit system

A policy of periodic replacement with minimal repair at failure is considered for the multi-unit system which have the specific multivariate distribution. Under such a policy the system is replaced at multiples of some period T while minimal repair is performed at any intervening component failures. The cost of a minimal repair to the component is assumed to be a function of its age and the number of minimal repair. A simple expression is derived for the expected minimal repair cost in an interval in terms of the cost function and the failure rate of the component. Necessary and sufficient conditions for the existence of an optimal replacement interval are exhibited.     

An Age-Based Inspection and Replacement Policy for Heterogeneous Components

This paper considers a hybrid maintenance policy for a single component from a heterogeneous population. The component is placed in a socket, and the component and socket together comprise the system. The $s$-population of components consists of two sub-populations with different failure characteristics. By supposing that a component may be in a defective but operating state, so that there exists a delay time between defect arrival and component failure, we consider a novel maintenance policy that is a hybrid of inspection and replacement policies. There are similarities in this approach with the concept of “burn-in” maintenance. The policies are investigated in the context of traction motor bearing failures. Under certain circumstances, particularly when the mixture parameter is large, and the distribution of lifetimes for the two component types are well separated, the hybrid policy has significant cost savings over the standard age-based replacement policy, and over the pure inspection policy. In addition to the cost metric, the mean time between operational failures of the system under the hybrid policy can be used to guide decision-making. This maintenance policy metric is calculated using simulation, and using an approximation which assumes that operational failures occur according to a Poisson process with a rate that can be calculated in a straightforward way. The simulation results show good agreement with the approximation.