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.     

Reliability and MTTF evaluation of a repairable complex system under waiting

This paper deals with the reliability and mean time to failure (MTTF) evaluation of a complex system under waiting incorporating the concept of hardware failure and human error. Failure rates of the complex system follow exponential time distributions, whereas repair follows a general repair time distribution. Laplace transforms of various state probabilities have been evaluated and then reliability is obtained by the inversion process. A formula for variance of time to failure has also been developed. A particular case is also given to highlight some important results. Moreover, various plots have been sketched at the end.     

IC长贮存寿命评价方法

高可靠长寿命产品在军事、航空航天、电子工业、通信等领域应用越来越广泛,如何保障其可靠性与预测其寿命是值得深入研究的重要问题。越来越多的单位,特别是航空航天系统的单位,对其选用的产品提出了具有32年贮存寿命要求的高可靠性指标。长寿命及超长寿命的电子元器件的贮存寿命评价是以加速试验为评价方法的。建立准确的失效机理及模型是评价正确与否的关键。文章通过收集大量高温贮存及常温贮存的实测数据,建立失效模型,推算出应力条件及相应的加速因子。文中实践证明,通过模型仿真出的贮存寿命具有高的可信度。     

A combined fuzzy-logic and physics-of-failure approach toreliability prediction

An original reliability prediction procedure is presented. The physics of failure accounts for the failure mechanisms involved (a lognormal distribution was presumed); the interactions (synergies) between the technology factors depending on the manufacturing techniques are considered. The basis of this methodology (called SYRP=synergetic reliability prediction) is the assessment of failure-risk coefficients (FRC), based on fuzzy logic, for the potential failure mechanisms induced at each manufacturing step. These FRC are corrected at the subsequent steps by considering the synergy of the manufacturing factors, At the end of the manufacturing process, final FRC are obtained for each potential failure mechanism; the parameters of the lognormal distribution are calculated with a simple algorithm. Experimental results for four lots of the same type of semiconductor devices, each lot being manufactured with a slightly different technology, were obtained. SYRP forecasts for these four lots agree well with accelerated life test results. This is a fairly good result, because SYRP was used early, at the design phase     

Accelerated stress testing of a-Si:H pixel circuits for AMOLED displays

Electronics reliability testing is traditionally carried out by accelerating the failure mechanisms using high temperature and high stress, and then predicting the real-life performance with the Arrhenius model. Such methods have also been applied to organic light-emitting diode (OLED) testing to predict lifetimes of tens of thousands of hours. However, testing the active matrix OLED thin-film transistor (TFT) backplane is a unique and complex case where standard accelerated testing cannot be directly applied. This is because the failure mechanism of pixel circuits is governed by multiple material and device effects, which are compounded by the self-compensating nature of the circuits. In this paper, we define and characterize the factors affecting the primary failure mechanism and develop a general method for accelerated stress testing of TFT pixel circuits in a-Si AMOLED displays. The acceleration factors derived are based on high electrical and temperature stress, and can be used to significantly reduce the testing time required to guarantee a 30 000-h display backplane lifespan.     

Estimation of system reliability for uncooled optical transmittersusing system reliability function

This paper investigates the system reliability for 155 Mb/s optical transmitters by deriving a system reliability function from reliability data of each component for transmitters, laser diode, photodiode, optical assembly, and driver IC. The reliability data for each component reliability function have been obtained from accelerated aging test. The reliability parameters such as failure rate, mean time-to-failure (MTTF), standard deviation are obtained from a probability plotting method. From the system reliability function, the MTTF of the optical transmitter at 65°C was estimated to be 47000 h with 95% confidence. In this estimation, we introduced modified lifetime of laser diodes and reliability function of optical assembly     

Approximated reliability of r-out-of-n(F) system with common cause failure and maintenance

In modern industries very high reliability system are needed. To improve the reliability of system, the component redundancy and maintenance of component or system play an impotant role and must be studied. This paper presents a reliability model of a r-out-of-n(F) redundant system with maintenance and Common Cause Failure. Failed component repair times are arbitrarily distributed. The system is in a failed state when r units failed because of the combination of single element failure or CCF(Common Cause Failure). Laplace transformation of reliability is derived by using analysis of Markov state transition graph. By using the analyzed MTBF, we compute MTBF of r-out-of-n(F) system. The MTBF with CCF is saturable even if repair rate is large.Approximated reliability of the r-out-of-n(F) system with maintenance and Common Cause Failure O.SummaryThe paper presents a reliability model of a r-out-of-n(F) redundant system with maintenance and Common Cause Failure. Failed component repair times are arbitrarily distributed. The system is in a failed state when r units failed because of the combination of single element failure or Common Cause Failure. Laplace transformation of reliability is derived by using analysis of Markov state transition graph. By analyzing this mean visiting time equations, we compute MTBF and shows computational example. The MTBF with CCF is saturable even if repair rate is large. In general the maintenance overcomes MTBF bounds, But the repair method not overcome the MTBF saturation when the system has Common Cause Failure.     

Issues in accelerated electromigration of solder bumps

The relentless progress of semiconductor integration is reducing the area required for circuits. As die size shrinks the area available for power and ground bumps on wafer-level chip-scale packages (WLCSPs) also shrinks and, with fewer power bumps, the bump current density is now approaching levels where electromigration is a significant reliability concern. Package designers need guidelines on the minimum number of power and ground bumps for a given application and reliability requirement.The failure rate due to electromigration depends on many factors such as alloy composition, operating temperature, and current density. Some of these have time-dependant components including grain structure, current distribution, and alloy component distribution. It has been found that these, in turn, are also dependent on other factors such as thermomigration and strain-induced coarsening.In such a dynamic system the time-dependant materials properties so obfuscate the extrapolation parameters as to render accelerated testing indeterminate.     

金属膜电阻失效前后概率分布及可靠性分析

产品在加工时总会有不可控的因素影响产品质量的稳定性,为解决这一问题,本文从可靠性分布函数的角度提出了提高电阻质量的方法。本文通过对金属膜电阻进行步进应力加速寿命试验以及电阻失效前后概率分布试验,得到了失效前后的阻值概率分布函数及正常应力下的概率分布函数与可靠性指标。实验结果表明,电阻阻值失效前后分布都属于威布尔分布。同时,给出了电阻损伤7.2%~15.6%,且失效模型为持续施加电压下不可逆的积累损伤模型时的分布函数,并获得了合格电阻与冒烟损坏电阻概率分布曲线的明显区别,从而,有可能从概率分布角度定义电阻的质量特性。     

Optimum Bivariate Step-Stress Accelerated Life Test for Censored Data

A step-stress accelerated life test for two stress variables is developed. The time to failure follows the Weibull distribution, and the test is subject to termination at a predetermined time, leading to censored failure data. An optimum test plan is developed to determine the test interval for each combination of stress levels. The scale parameter of the Weibull distribution for each combination of stress levels is defined as a log linear function of the stress levels. The optimal criterion is defined to minimize the asymptotic variance of the maximum likelihood estimator of the life for a specified reliability     

Physical Analysis of Stress Testing for Failure of Electronic Components

Starting with an assumption concerning the type of physical process causing failure and an assumption concerning the random distribution of components with respect to a failure threshold. cumulative distribution functions in time, temperature, and voltage are derived. These cumulative distribution functions are identical to each other if the random variables are certain functions of time, temperature, or voltage, thus showing the equivalence of time, temperature, and voltage as stresses. The cumulative distribution function in time is the familiar log-normal function. If it is known that the assumed physical process is the only one causing failure, then one can rigorously replace time by temperature or voltage. However, it is demonstrated that in an accelerated test, i.e., one in which time is replaced by another stress such as temperature, one can never be sure that another process will not be predominant at longer times; thus, one can never make a certain extrapolation to longer times. One might be able to circumvent this difficulty by having a thorough knowledge of the physics, chemistry, and metallurgy of the possible failure processes in the component.     

功率型白光LED可靠性的实验及仿真建模研究

快速推广LED产品到照明市场最主要的障碍在于长期的可靠性测试问题。由于长期的LED可靠性测试不符合快速且低成本的要求,因此本实验对白光LED进行步进式加速寿命老化测试,步进式环境温度从55oC到145oC变化。同时,对LED进行结温测试,并使用COMSOL仿真软件进行温度场分布仿真来模拟器件的发热情况,结果表明荧光胶处的温度高于LED芯片温度。在长期老化之后,对LED的光度进行测量,可以对LED的失效机理进行分析。通过研究温度对LED的光谱功率分布衰减的影响及光通量衰减的影响,发现在经过近3500 h的老化之后,LED的光衰很严重,表明电流及高温对LED的影响是极大的。     

Une modelisation bayesienne du taux de defaillance en fiabilite

The classical approach in reliability in which no difference is made between the failure rates of various electronic components making up an assumed homogeneous batch, leads to some formal difficulties which will be demonstrated. A new approach is proposed in which each component in the batch is characterized by its own “stress resistance capability”. This approach leads us to postulate the existence of an individual “lambda” attached to each component and thus that of a statistical distribution of the “lambdas” at batch level. Taking this distribution as a distribution a priori, a bayesian treatment is then applied. The result is a formalisation of an unconditional failure rate reflecting the mean failure rate of the batch considered. Choosing a priori a gamma type distribution (justified by reasons of a practical and theoretical nature), it will be shown that the unconditional failure rate decreases hyperbolically with time. Consequently, a new “bath-curve” profile is obtained in which the horizontal line becomes slightly inclined. Lastly, the proposed model reveals a simple relationship between the burn-in time for a batch of components and the unconditional failure rate of the same batch after burn-in.     

Reliability comparison of 28 V–50 V GaN-on-SiC S-band and X-band technologies

This paper discusses the reliability performance of Wolfspeed GaN/AlGaN high electron mobility transistor (HEMT) MMIC released process technologies, fabricated on 100 mm high purity semi-insulating (HPSI) 4H-SiC substrates. The intrinsic reliability performances of the 28 V and 40 V technologies, with 400 nm and 250 nm gate length, have been characterized with DC accelerated life test (DC-ALT), for which ohmic contact inter-diffusion is the wear-out mechanism, and is accelerated by temperature and current. The intrinsic reliability performance of the 50 V technologies, with 400 nm gate length, have been characterized with RF-ALT, for which source-connected second field plate void coalescence is the wear-out mechanism which is accelerated by temperature. In spite of the differences in the accelerated test methodologies and wear-out mechanisms, all of the Wolfspeed GaN-on-SiC technologies demonstrate high and similar predicted lifetimes at their respective maximum recommended operating conditions. The reliability performance is supported with successful technology qualifications with zero failures, and volume manufacturing with a demonstrated low field failure rate.     

威布尔分布下VFD恒定应力加速寿命试验与统计分析

为了精确地估计真空荧光显示器(VFD)的可靠性寿命,节省试验测试时间,通过建立加速寿命试验模型开展了4组恒定应力加速寿命试验,采用威布尔函数描述VFD寿命分布,利用最小二乘法(LSM)估计威布尔参数,完成了试验数据的统计分析,并自行开发了寿命预测软件,确定了加速寿命方程,实现了VFD的寿命估计。数值结果表明,试验设计方案是正确可行的,VFD的寿命服从威布尔分布,其加速模型符合线性阿伦尼斯方程,每个加速应力水平下VFD的失效机理不变,精确计算出的VFD寿命对其生产厂商和技术人员具有重要的指导意义。     

Microprocessor and LSI Microcircuit Reliability-Prediction Model

This paper discusses the development of an improved failure-rate prediction method which can be used to assess the reliability of complex and new-technology microcircuits, especially memories, microprocessors, and their support devices. The prediction models are similar to those presented in MIL-HDBK-217C with several modifications to reflect the variation of reliability sensitive parameters and to discriminate against the device design and usage attributes which contribute to known failure mechanisms. A comparison of the failure rate predictions calculated using MIL-HDBK-217C and the actual failure rates for LSI random logic and memory devices did not indicate a reasonable correlation. An analysis of the 217C models revealed that the lack of correlation was attributable to the generic consolidation of model parameters, which ultimately reduced model sensitivity to several critical reliability factors. The model accuracy was greatly improved, without substantially increasing model complexity, by separating some generic parameters into sets of more detailed parameters. The major model revisions included: ? Complexity factors oriented toward major device function and technology categories ? Development of temperature factors for each device technology, in both hermetic and nonhermetic packages ? Introduction of an additive package failure-rate factor based upon package type and number of functional pins ? Introduction of a voltage derating stress factor for CMOS devices with maximum recommended operating supply voltage greater than 12 volts ? Introduction of a ROM and PROM programming technique factor to reflect the influence of the programming mechanism used in these devices.     

温度传感器失效机理分析

通过对汽车用NTCR式温度传感器失效样品的测试、分类和解剖 ,发现有 4类可能的失效模式 ;在模拟试验的基础上 ,分别对各类失效样品进行了失效机理分析 ,并对如何提高这种传感器的可靠性提出了改进建议。     

Reliability life-testing and failure-analysis of GaAs monolithicKu-band driver amplifiers

`Gallium-arsenide monolithic microwave integrated-circuit (MMIC) Ku-band driver amplifiers were life tested under accelerated high temperature, DC and RF conditions until failure. These MMIC are used in various applications such as radar and satellite communication systems. The failure mechanisms controlling their reliability must be understood in order to improve the lifetime for these and other applications. This paper discusses the experimental procedures, statistical evaluation of the data and failure analysis of the devices. To the authors' knowledge, this is the first report of RF life testing of dual-gate driver amplifiers. The majority of the devices failed catastrophically due to high drain current, while others failed parametrically due to low output power. Failure analysis indicates that degradation of the Si₃N₄ dielectric layer to be the main failure mechanism in these MMIC. Statistical analysis revealed an activation energy of 0.87 eV and a median lifetime of 5.8·10⁴ hours at 140°C channel temperature, which is consistent with surface-phenomena failure mechanisms     

C波段功率GaAs MESFET的可靠性

本文通过功率GaAs MESFET的筛选与环境、寿命试验阐述了器件的早期失效模式模型,估计了可靠性水平,指出了主要失效因素,并用实验方法讨论了突变烧毁失效,分析了失效原因,探讨了提高可靠性的途径。