Maturity Factors in Predicting Failure Rate for Linear Integrated Circuits

There are differences between failure rates obtained from test results, and failure rates obtained from the failure rate models. In some cases, failure rates obtained from failure rate models are 10 to 50 times larger (worse) than failure rates obtained through testing of the same devices. This indicates that the available failure rate models need some modification. It is not the intent of this paper to disqualify the available failure rate models. This paper suggests only that the available failure rate models be modified by including two maturity factors: ? date code factor (technology maturity in general) ? manufacturer's factor (maturity of specific manufacturer) This paper is based on tests performed on more than 18000 linear ICs (integrated circuits) manufactured by National Semiconductor and on comparative tests performed on more than 2500 linear parts from other IC manufacturers. This paper offers date code factors which could be used in prediction of failure rates for linear IC's. It also offers manufacturer's factor for devices manufactured by National Semiconductor. However, offered date code factors and manufacturer's factor are only indicative, and given values should be confirmed or improved by further investigations. This paper deals mostly with prediction of failure rates for linear ICs. But the same approach for developing date code factors and manufacturer's factors could be used for developing similar factors for other ICs (besides linear), and for other manufacturers.     

Reliability Enhancement Through Optimal Burn-In

Burn-in is an important screening method used in predicting, achieving, and enhancing field reliability. Although electronics burn-in has been studied qualitatively, no comprehensive quantitative approach exists for determining optimal burn-in periods. This paper presents a cost-optimization model from a system viewpoint, with burn-in periods for the components as the decision variables. This model is applied to an electronic product recently developed which uses many ICs. State-of-the-art ICs have high early-failure rates and long infant mortality periods. Proper use of burn-in reduces early failure rates and reduces system deployment costs. The total cost to be minimized is formulated as a function of the mean costs of the component, device burn-in, shop repair, and field repair, which in turn are functions of the mean number of failures during and after burn-in. Component and system reliability are constraints that have to be satisfied. The early device failures are assumed to have a Weibull distribution. The formulated problem, with failure rates and cost factors, is optimized. Some basic properties of reliability and cost functions are discussed.     

浅谈对集成电路加速寿命试验的认识

老炼、稳态寿命等加速寿命试验是衡量集成电路使用寿命的主要手段。文中简要介绍了集成电路的主要可靠性指标——FIT,呈现集成电路失效特征的"浴盆曲线",以及不同失效阶段的主要影响因素、失效率与时间相关的统计分布特征。在此基础上,文章对老炼和稳态寿命的试验目的进行了说明,并列出稳态寿命试验的等效试验条件表以及通过该试验的集成电路使用寿命的一些参考数据。     

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.     

Analysis of burn-in time using the general law of reliability

Empirical lifetime distributions sometimes have a bathtub-shaped failure rate. This paper deals with some models having a bathtub-shaped failure rate. The root-mean-square criterion is proposed for selection of the best model. Besides two criteria of optimum burn-in time are proposed. The comparison of some models with the general law of reliability is given to determine a burn-in time in a number of examples.     

电子元器件老炼试验技术

老炼是对电子元器件施加应力,剔除有缺陷的元器件的过程。长时间的老炼会对一些原本健康的器件寿命产生影响,但是时间过短却又不能起到很好地剔除有缺陷的元器件的目的。在相关文章的基础上总结了哪类电子元器件适合进行老炼,以及元器件老炼时间的优化问题,提出电子元器件老炼的3个准则,电子元器件最优老炼时间的确定问题,以及元器件老炼发展方向。     

On optimal burn-in procedures - a generalized model

Burn-in is a manufacturing technique that is intended to eliminate early failures. In this paper, burn-in procedures for a general failure model are considered. There are two types of failure in the general failure model. One is Type I failure (minor failure), which can be removed by a minimal repair or a complete repair; and the other is Type II failure (catastrophic failure), which can be removed only by a complete repair. During the burn-in process, two types of burn-in procedures are considered. In Burn-In Procedure I, the failed component is repaired completely regardless of the type of failure; whereas, in Burn-In Procedure II, only minimal repair is done for the Type I failure, and a complete repair is performed for the Type II failure. Under the model, various additive cost functions are considered. It is assumed that the component before undergoing the burn-in process has a bathtub-shaped failure rate function with the first change point t/sub 1/, and the second change point t/sub 2/. The two burn-in procedures are compared in cases when both the procedures are applicable. It is shown that the optimal burn-in time b/sup */ minimizing the cost function is always before t/sub 1/. It is also shown that a large initial failure rate justifies burn-in, i.e., b/sup */>0. The obtained results are applied to some examples.     

A nonparametric approach to estimate system burn-in time

System burn-in can get rid of more residual defects than component and subsystem burn-ins because incompatibility exists not only among components, but also among different subsystems and at the system level. There are two major disadvantages for performing the system burn-in: the high burn-in cost and the complicated failure rate function. This paper proposes a nonparametric approach to estimate the optimal system burn-in time. The Anderson-Darling statistic is used to check the constant failure rate (CFR), and the pool-adjacent-violator (PAV) algorithm is applied to “unimodalize” the failure rate curve. Given experimental data, the system burn-in time can be determined easily without going through complex parameter estimation and curve fittings     

Bathtub failure rate and upside-down bathtub mean residual life

This paper shows that: (1) the mean residual life (MRL) of a component has an upside-down bathtub-shape if the component has a bathtub-shape failure-rate function, but the converse does not hold; and (2) there is an optimal burn-in policy to maximize the MRL when the underlying lifetime distribution has a bathtub-shape failure rate     

Minimizing cost-functions related to both burn-in and field-operation under a generalized model

Summary and Conclusions-Burn-in is a method used to improve the quality of products. In field operation, only those units which survived the burn-in procedure will be used. This paper considers various additive cost structures related to both burn-in procedure and field operation under a general failure model. The general failure model includes two types of failures. Type I (minor) failure is removed by a minimal repair, whereas type II failure (catastrophic failure) is removed only by a complete repair (replacement). We introduce the following cost structures: (i) the expenses incurred until the first unit surviving burn-in is obtained; (ii) the minimal repair costs incurred over the life of the unit during field use; and (iii) either the gain proportional to the mean life of the unit in field operation or the expenditure due to replacement at a catastrophic failure during field operation. We also assume that, before undergoing the burn-in procedure, the unit has a bathtub-shaped failure rate function with change points t/sub 1/ & t/sub 2/. The optimal burn-in time b/sup */ for minimizing the cost function is demonstrated to be always less than t/sub 1/. Furthermore, a large initial failure rate is shown to justify burn-in, i.e. b/sup */>0. A numerical example is presented.     

A Model for Burn-In Programs for Components with Eliminateable Defects

We consider a component with a random number of defects which can be discovered and corrected during the course of a burn-in program. The failure rate after burn-in is constant (in time) and depends on the number of remaining defects. A sufficient condition is given for a burn-in program to lead to increased mean time to failure; it is given in terms of the prior distribution of the number of defects and the failure rates.     

A relation model of gate oxide yield and reliability

The relationship between yield and reliability is obviously important for predicting and improving reliability during the early production stage, especially for new technologies. Previous research developed models to relate yield and reliability when reliability is defined as the probability of a device having no reliability defects. This definition of reliability is not a function of mission time and thus is not consistent with reliability estimated from the time-to-first-failure data which is commonly used. In this paper, we present a simple model to tie oxide yield to time-dependent reliability by combining the oxide time to breakdown model with a defect size distribution. We show that existing models become special cases when a single mission time is considered. As the proposed reliability function has a decreasing failure rate, the result is useful for a manufacturer seeking to find an optimal burn-in policy for burn-in temperature, burn-in voltage, and burn-in time.     

Correlation Between Laboratory Test & Field Part Failure Rates

In Japan, failure rates for non high-reliability electronic parts, obtained from laboratory tests, are generally about ten times those obtained in the field. The reasons for this difference have been analysed by using part failure-rate data collected from major part suppliers, equipment manufacturers, and public users in Japan. This paper numerically analyses transistor data. The two main causes of the difference between laboratory and field failure rates are 1) the difference in failure criteria between them and 2) unreasonable use of the constant failure rate without actually determining the real failure rate. By using the conversion factors, it is possible to predict electronic equipment MTBF by using laboratory failure rates with appropriate application factors pertaining to whether the units are in use on a ship board, airborne, etc. basis. Failure rates for the electronic parts with unsatisfactorily long burn-in time lapse must be treated as carefully as the rate data published in the AIST data.     

Comparison of reliability impacts of two active power curtailment methods for PV micro-inverters

The future generation of solar PV inverters will have to be equipped with new grid supporting functionalities. One of them is the active power curtailment (APC) for overvoltage prevention. New functionalities can be challenging from the design-for-reliability aspect. This is especially true for micro-inverters, due to their outdoor application and more extreme environmental conditions. In this paper, two APC designs are considered and their impact on component reliability is predicted using 217Plus™ empirical method. The analyzed components are DC bus capacitors, DC–DC MOSFETs and an AC protection relay. The study reveals that APC can decrease the failure rate of MOSFETs and capacitors. Depending on the selected APC method the capacitor failure rate reduction is either 6% or 54%, but the latter benefit comes with a trade-off for a high failure rate increase of the AC relay. The failure rates are not significant from warranty perspective, but indicative enough for making preliminary design-for-reliability recommendations.     

Optimal burn-in for minimizing cost and multiobjectives

In general, a small proportion of components will be weak because of some imperfection in the control of the production process or in the design of the components. This paper discusses an optimal burn-in procedure to minimize total costs based on the assumption that some of the components are weak and deteriorate faster than the strong components. The procedure will define the costs of burn-in errors. In practice, it may be impossible to eliminate all weak components through burn-in due to a nonzero proportion of defectives of the components. Therefore, burn-in errors could occur for some reasons. Probability models and cost models are formulated to find the optimal burn-in time that minimizes the expected total cost. An example is included to show how to use the results. Finally, multiobjective optimal burn-in for series systems is presented using the surrogate worth trade-off method.     

An extended model for optimal burn-in procedures

In this paper, the problem of determining optimal burn-in time is considered under the general failure model. There are two types of failure in the general failure model. One is Type I failure (minor failure) which can be removed by a minimal repair, and the other is Type II failure (catastrophic failure) which can be removed only by a complete repair. In the researches on optimal burn-in, the assumption of a bathtub shaped failure rate function is commonly adopted. In this paper, upper bounds for optimal burn-in times are obtained under a more general assumption on the shape of the failure rate function, which includes the bathtub shaped failure rate function as a special case.     

Burn-in effect on yield

By removing infant mortalities, burn-in of semiconductor devices improves reliability. However, burn-in may affect the yield of semiconductor devices since defects grow during burn-in and some of them end up with yield loss. The amount of yield loss depends upon burn-in environments. Another burn-in effect is the yield gain. Since yield is a function of defect density, if some defects are detected and removed during burn-in, the yield of the post-burn-in process can be expected to increase. The amount of yield gain depends upon the number of defects removed during burn-in. In this paper we present yield loss and gain expressions and relate them with the reliability projection of semiconductor devices in order to determine burn-in time     

Investigation of Arrhenius acceleration factor for integrated circuit early life failure region with several failure mechanisms

Use of the Arrhenius equation for analysis of burn-in and life test data has been called into question in recent years. Validity of the Arrhenius activation energy is asserted to be restricted to only one failure mechanism. Therefore, if multiple failure mechanisms apply to an integrated circuit type, the temperature acceleration factor must be complex. In this study a model is constructed using the Weibull distribution for the failure rate applicable when there are multiple failure mechanisms. In this model a different Arrhenius activation energy corresponds to each failure mechanism. It is shown that under conditions expected to be valid for most integrated circuits, an empirical effective Arrhenius activation energy can be computed that is valid for life test data taken under typical conditions to better than 10%. This provides some justification for the continued usage of a simple Arrhenius equation as an empirical model to analyze life test data.     

A Quantitative Analysis of Semiconductor Device Failure Rates as Graphically Indicated in Military Handbook 217

A graphical presentation of semiconductor device failure rates is made in Figs. 13B and 14B of Mil-Hdbk-217 (see Figs. 1 and 2). From this presentation, Equations may be derived which indicate interesting properties, to failure physicists, device engineers, and equipment designers. On the basis of the equations it may be concluded that: (1) extrapolating room temperature failure rates from failure rates of devices stored at elevated temperatures is not likely to be meaningful; (2) there is a definite relationship between storage failure rate and failure rate in actual use (in the temperature range of interest); (3) the storage failure rate is large enough at normal storage temperatures so that, if semiconductor device failure rates influence the reliability of equipment in which they are used, they will contribute significantly to the finite storage life of the equipment (another way of expressing the last statement is that a manufacturer with a large storage inventory of semiconductors will find a significant decrease in the percentage of usable devices with time);(4) there are some instances (as delineated earlier by equations), when increasing the number of semiconductor devices and dividing the load proportionately improves reliability, and there are other cases when it does not. While the analysis makes no claim as to the validity or accuracy of Figs. 1 and 2, the mathematics permits statements about conditions necessary to confirm the data.     

提高LTE网络RRC连接建立成功率方法研究

LTE网络较2G、3G网络最大的优势在于为用户提供更高速率。然而无线小区资源是一个共享资源,在同一个小区里,因某些突发因素,当用户数逐渐增多时,每个用户获得的速率将逐渐下降。当用户超过系统容量时,可能导致部分用户无法接入,大量用户同时接入网络将可能出现RRC连接建立失败次数增多,导致RRC连接建立成功率降低、用户感知差。本文通过研究异频负载均衡、接入限制控制和大容量保障相关参数,总结出应对大量用户聚集场景,避免RRC连接建立失败的方法。