Analysis of reliability data for mechanical systems

World Abstracts on Microelectronics and Reliability 146 (1991). For the extreme value distribution, the maximum likelihood method does not provide explicit estimators for the location and scale parameters. This paper provides a method of deriving explicit estimators by approximating the likelihood function. We derive the asymptotic variances, covariance, and conditional bias of these estimators, and show that they are almost as efficient as the maximum likelihood estimators and just as efficient as the best linear unbiased, and the best linear invariant estimators. Two examples illustrate this method of estimation. A generalized reduction method for the connectedness probabmty of stochastic networks. F. BEICHELTand P. TITTMANN. 1EEE Trans. Reliab. 40(2), 198 (1991). The connectedness probability of a stochastic network is computed by a generalized approach to network reduction. The new approach is based on separating-vertex-sets and on introducing more than one replacement graph. Computational aspects are discussed and examples are presented. Investing in product assurance to ensure that: better is not the enemy of good. DOUGLASP. EBERHARD,MARKVISBISKYand KENNETH C. SYRACUSE.Proc. A. Reliab. Maintainab. Symp., 70 (1991). High reliability products, such as the lithium/ iodine battery used to power implantable cardiac pacemakers, require programs to assure that progress changes which are suggested as the product matures do not degrade reliability. A comprehensive process validation program can assure that process changes are smoothly introduced into production with confidence that reliability has not been adversely affected. This program involves prototype builds, process validation builds, reliability and quality assessment, sensitivity analysis, rational tolerancing, capability analyses, search for sources of variation, and follow-up analyses. This comprehensive approach was successfully applied to the process validation of the substrate anode coating method. The result is the manufacture of a battery which continues the tradition of high-reliability, exhibits reduced cell-to-cell performance variability, and is more efficient to manufacture. Dynamic batching heuristic for simultaneous processing. C. ROar,R GLASSEY and W. WILLIEWENG. IEEE Trans. Semicond. Mfg 4(2), 77 (1991). Batch processing plays an important role in several production industries including semiconductor manufacturing. In a computer integrated manufacturing (CIM) system environment, it is possible to predict the arrival epoches of incoming lots at each work station. It is demonstrated how to use the forecasting information to reduce the average waiting time of lots arriving at a batch work station. Robustness of a semi-parametric proportional intensity model. THOMAS L. LANDERS and HOMA E. SOROUDI. IEEE Trans. Reliab. 40(2), 161 (1991). The Prentice, Williams, Peterson (PWP) semi-parametric model for the failure processes of repairable systems involves regression on explanatory variables, across strata defined by the failure-event count. We developed a heuristic method for assessing the robustness of the PWP model, where the true underlying process is nonhomogeneous Poisson with power-law intensity function. The PWP model performed well for large samples and increasing rates of occurrence of failures and poorly for small samples and decreasing rates of occurrence of failures. Application of the atomic force microscope to integrated circuit reliability and failure analysis. MARK R. RODGERS. IEEE/IRPS, 250 (1991). As integrated circuit (IC) geometries contine to shrink, and smaller defects affect performance and reliability, ultra-high resolution measuring technologies are becoming increasingly important. The

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atomic force microscope (AFM)--which is now available commercially--offers three-dimensional surface measurement capability from angstroms to over 100 microns, the ability to image insulators directly without coating, and minimal sample preparation. These features indicate strong potential for applications in IC failure analysis and refiability, particularly as ICs move toward submicron geometries. A class of tests for testing an increasing failure-rate-average distribution with randomly fight-censored data. MARTIN T. WELLS and RAM C. TIWARI. IEEE Trans. Reliab. 40(2), 152 (1991). For testing exponentiality vs (nonexponential) increasing failure rate average alternatives using the randomly right censored data, a class of test statistics based on a functional of the Kaplan-Meier estimator is proposed. The asymptotic relative efficiencies of tests from this class with respect to other test statistics are derived. The efficiency loss due to censoring is studied. The proposed tests are applied to published survival data. Analysis of refiabifity data for mechanical systems. WILLIAM B. CLARK. Proc. A. Reliab. Maintainab. Syrup., 438 (1991). This paper presents case studies on the analysis of reliability data for complex hydro-mechanical systems. The case studies indicate that failure rate is dependent on unit age, and that system reliability is usually limited by a few dominant failure modes which exhibit an increasing failure rate with age (wearout). Unless this characteristic of mechanical systems is recognized and made a part of the hypothesis for the analysis, the results are likely to be in error. One important technique in an analysis is a Weibull plot of the data. Observation of such a plot will reveal changes in failure rate with age as well as the basic failure rate characteristic. The paper also references an analysis technique using the combination of two Weibull plots to model complex hydro-mechanical system failures called the BiWeibull. A new failure mechanism related to grain growth in drams. T. KATAVAMAet al. IEEE/IRPS, 183 (1991). A cell plate leakage phenomenon which degrades retention time was investigated in a DRAM with planar cells. It was found that the leakage phenomenon is a new failure mode related to grain growth of polycrystalline silicon under oxidationinduced compressive stress. Localized stress causes irregular grain growth and the development of a protuberance of silicon, resulting in the capacitor gate-oxide leakage. Building-in reliability: making it work. HARRY A. SCHAFFT, DAVID A~ BAGLEEand PATRICK E. KENNEDY. IEEE/IRPS, 1 (1991). Aggressive reliability and market-entry demands will require the use of a building-in approach to reliability. To adopt this approach and make it work requires that very significant breaks are made from the traditional ways of improving and appraising reliability. The nature of these breaks are discussed in the context of describing the basic elements of the approach of building-in reliability and the obstacles that hinder its adoption. To help visualize how the approach can be implemented, initial steps to make the transition and some specific examples of its use are described. Reliability prediction, in the conceptual phase, of a processor system with its embedded software. H. B. CH~NOWETH. Proc. A. Reliab. Maintainab. Symp., 416 (1991). In the last two decades, computers and their associated software (including microcoded devices) have required a reliability prediction methodology during concept trade-off studies. A method has been developed to predict the software reliability in processor applications based on concept parameters and